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in  2009  witii.  funding  from 

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:/ 


Bulletin  No.  20.  V.  l'.  P. -72. 

U.S.  Dl^PARTMEN'r   OF  A(  iRICUL'I  URl^:. 

DIVISION  OF  VEGETABLE  PHYSIOLOGY  AND  PATHOLOGY. 

B.    T.    GALL-OWAY,    Chief. 


F'EACH   leaf  CURL: 


ITS  NATURE  AND  TREATMENT. 


BY 


NE^VTO]S^    B.   -ELEnOE, 

In  Charge  of  Pacific  Coast  Laboratory,  Santa  Ana,  California, 


WASHINGTON: 

(JOVKRNMENT     PRINTING     OFFICE, 
1000 


DIVISION  OF  VEGETABLE  THYSIOUKa   AM)  PATHOLOUY. 


SCIENTIFIC  STAFF. 

B.  T.  Galloway,   ('///(/  oj  Division. 
Albert  F.  Woods,  Assistant  Chief. 

ASSOCIATES. 

Erwin  F.  Smith,  .  V.  H.  Dorsett, 

Merton  B.  Waite,  Oscar  Loew, 

Newton  B.  Pierce,  Wm.  A.  Orton, 

Herbert  J.  AVebber,  Ernst  A.  Bessey, 

M.  A.  Carleton,  Flora  W.  Patterson, 

Marci's  L.  Floyd.* 

IN  charge  of  laboratories. 

Albert  F.  Woods,  J'huit  Physiology. 

Erwin  F.  Smith,  Plant  Patltoh)(/y. 

Newton  B.  Pierce,  Pacific  Coast  Lahoralory. 

Herbert  J.  Webber,  Plant  Breedimj. 

Oscar  LoEW,t  Plant  Xutrition  and  Fcnncntalion. 

*Di'taik'cl  ii.s  tobacco  expert,  Divi.sion  of  Soils. 

+In  charge  of  tobacco  fermentation  investigations,  iJivisiun  of  Soils. 


LlHTIiR  OF  FRAXSMITTAL 


U.  S.  Department  of  A(;rk  ultuhe. 
Division  of  Vegetable  Physiology  and  Pathology, 

Washington,  B.  C,  February  W,  1900. 
Sir:  I  rospectfully  transmit  herewith  a  report  on  peach  leaf  curl, 
prepared  by  Mr.  Newton  B.  Pierce,  who  has  charge  of  the  work  of 
this  Division  on  the  Pacific  coast,  and  recommend  that  it  be  published 
as  Bulletin  No.  20  of  the  Division.  The  report  embodies  the  results 
of  investigations  and  experiments  carried  on  for  a  number  of  3'ears, 
and  shows  conclusively  that  peach  leaf  curl  can  be  controlled  by  com- 
paratively simple  and  inexpensive  treatment. 
Respectfully, 


Hon.  James  Wilson, 

Secretary  of  Agriculture. 


B.  T.  Galloway, 

Chief  (f  Division. 


3 


LIHTER  OF  SURMITTAL 


Pacific  Coast  Laboratory, 

Santa  Ajui^  Cal.,  Decemher  15^  1899. 
Sir:  I  herewith  .sul)init  u  report  of  investigations  on  the  nature  and 
treatment  of  peach  leaf  curl.  The  experiments  described  were  con- 
ducted under  the  most  varied  conditions  of  soil,  climate,  etc.,  in  all  the 
leadinu-  peach  centers  of  the  United  vStates,  and  it  is  ])elieved  that  the 
recommendations  for  treatment  here  given  are  ecjually  applicable 
wherever  peaches  are  grown. 

Respectfully,  Newton  B.  Piercp:, 

III  Charge  of  PacljiG  Coast  Litlxiraton/. 
Mr.  Vi.  T.  Galloway, 

Chief.,  Division  <f  Veijetahle  Plajsiologij  and  Pafhalogij. 


CONTIiNTS. 


CnAITKR    I. PkIMAKY  CoNSII)P:K.\TIONS    IflCI.ATIVi;  to    riCACII     l.KAF  ClKI 11 

Introduction 11 

General  cluiract eristics  of  the  disease 12 

Geographic  distribution 12 

Origin  of  the  disease 1  ,S 

Losses  from  the  disease 1  !> 

Chapter  II. ^Nature  of  Peach  Leaf  Curl 22 

~  ^  Physical  conditions  influencing  the  disease 22 

The  fungus  causing  the  disease ?>\ 

H     Relations  of  the  fungus  to  the  host 40 

Chapter  III. — ^History  of  the  Treatment  of  Peach   Leaf  Ctrl 46 

The  European  situation 4(3 

^  Development  of  the  present  methods  of  treatment 48 

Chapter  IV. — Plan  of  Preventive  Spray  Work  Conducted  hy  the  Depart- 
ment   67 

Preliminary  plans  for  the  work 67 

Sl)ray  work  conducted  in  1894 70 

Spray  work  conducted  in  1 895 72 

General  consideration  of  sprays  applied 75 

Chapter  Y. — Influence  of' Sprays  on  the  Vegetation  of  the  Trees 77 

+-  Saving  of  foliage  from  injury  by  curl 77 

Comparisons  of  weight  and  color  of  foliage  from  sprayed  and  unsprayed  trees .  88 

-\-   Growth  of  branches  and  leaf  buds  on  sprayed  and  unsprayed  trees 91 

The  development  of  new  fruit  buds  and  fruit  spurs  for  the  year  following 

an  attack  of  curl 95 

Chapter  VI. — Influence  of  Sprays  on  the  Fruiting  of  the  Trees lO."! 

Thinning  the  fruit  of  sprayed  trees lO;? 

Gathering  fruit  of  sprayed  and  unsprayed  trees 1  OH 

-V- Comparative  quantity,  quality,  and  cash  value  of  fruit  from  sDrayed  and 

unsprayed  trees 112 

Comparati-ve  value  of  sprays  in  relation  to  fruit 115 

"Y- Comparative  size  of  fruit  on  sprayed  and  uns2)rayed  trees II li 

Color  of  sprayed  and  unsprayed  fruit 1 20 

Method  of  thinning  and  cost  of  picking  peaches 121 

Thinning  ])y  hand  and  by  curl 121 

Cost  of  picking  peaches 1 22 

The  local  action  of  curl  on  foliage  and  fruit 122 

-^-  Records  of  trees  sprayed  on  one  siile 122 

Chapter  VII. — Preventive  Spray  Work  Conducted  by  One  iiakdists 126 

General  consideration  of  the  auxiliary  work 126 

Notes  on  the  auxiliary  experiments  in  Michigan 127 

Notes  on  the  auxiliary  experiments  in  Oregon 135 

Notes  on  the  auxiliary  experiments  in  California 140 

Notes  on  the  auxiliary  experiments  in  New  York,  Indi.xua,  and  other 

peach-growing  States 144 

7 


8  CONTENTS. 

Page. 
Chapter  VIII. — Preparation,   Composition,   and  General    ('iiaracter.s  of 

THE  Sprays  Used 146 

Preparation  of  the  copper  sprays 146 

Copper  sulphate  solution '. 147 

Bordeaux  mixture 1 49 

Eau  eeleste ]  52 

Modified  eau  celeste 1 53 

Ainnioniacal  copper  carbonate 1 53 

i^Prei)aration  of  the  8uli)hur  sprays 154 

Preparation  of  combined  copper  and  sulphur  sprays  and  iKites  on  other 

sprays  tested 1 61 

Bordeaux  mixture  and  snli)hur  s^jrays  combined 161 

Miscellaneous  sprays 161 

General  characters  of  the  sprays  tested 162 

The  enduring  qualities  of  the  sprays 162 

The  corrosive  action  of  the  sprays 164 

Advantages  of  discernible  and  indiscernilile  sprays 165 

\l   Sprays  adapted  to  use  in  wet  and  in  dry  localities . .  166 

Chapter  IX. — The  Application  of  Sprays 167 

General  accessories  for  winter  spraying 167 

Nozzles  suited  to  winter  work 167 

Hose  and  extension  pipes 169 

Protection  of  the  sprayer 1 70 

Pumps  for  various  sized  orchaiils 171 

Spraying  tanks 175 

^-Applying  winter  sprays  for  curl 175 

.  .  The  time  for  winter  spraying 1 76 

Y  The  manner  of  applying  winter  spi-ays 1 7() 

Si>raying  where  other  diseases  a.re  present  with  curl 1 77 

Prune  rust  on  the  peach  {Puccinia  pnmi  Pers. ) 177 

Mildew  of  the  peach  {Podosphveva  uxyacanthx  De  B.) 1 78 

Brown  rot  of  the  peach  {Monilid  frudigena  Pers.) 178 

Black  spot  of  the  peach  {Chtdos^porium  mrpoph'dmn  Thi'im. ) 1 78 

Winter  blight  of  the  peach  and  other  spot  and  shot-hole  diseases,  such 

as  Phylloxttda  rircumsrissd 3erk.,  Ccrcospora  clr(niiiifiriK.s(i  Sacc.,  etc..  179 

Sooty  mold  of  the  ])each 1 79 

Animal  parasites  of  the  peach  tree ISO 

Chapter  X. — Nature  and  Source  of  the  Sprayin(;  Materials  Used 181 

Copper  sulphate 181 

Copper  carbonate 183 

Ammonia 1 85 

Sodium  carbonate 187 

Sulphur 190 

Chapter  XL — Peach  Varieties  and  Nursery  Stock  in  Relation  to  Cirl.  194 

Comparison  of  peach  varieties 194 

H  Treatment  of  nursery  stock 200 

Suminarv _  202 


ILLUSTRATIONS. 


PLATES. 

Page. 

Plate    I.  Curl-iiifcstod  peach  shoot  from  Biggs,  Cal 11 

II.   MyreHuiii  of  KruitKCHft  defonnan — the  fungus  causing  peach  leaf  cui-l .  35 

III.  Fruiting  stages  of  Exonscus  deforniunts 36 

IV.  Germination  of  the  ascospores  of  Eruascus  deJoviiKWK. 38 

V.  Terminal  peach  twigs  infested  with  peach  leaf  curl 42 

VI.  Sprayed  and  misprayed  peach  branches - 42 

VII.  Sprayed  and  unsprayed  Crajvfords  Late  trees,  Live  Oak,  Cal 77 

VIII.  Unsprayed  trees  in  Lovell  orchard.  Biggs,  Cal 89 

IX.  Lovell  trees  sprayed  with  Bordeaux  mixture,  Biggs,  Cal 89 

X.  Fruit  produced  by  row  15,  experiment  block.  Biggs,  Cal 107 

XL  Lovell  trees  sprayed  with  sulphur,  lime,  and  salt.  Biggs,  Cal 112 

XII.  Lovell  trees  sprayed  with  sulphur  and  lime.  Biggs,  Cal 112 

XIII.  Lovell  trees  sprayed  with  Bordeaux  mixture.  Biggs,  Cal 115 

XIV.  Lovell  trees  sprayed  with  eau  celeste,  Biggs,  Cal 115 

XV.  Lovell  trees  sprayed  with  modified  eau  celeste,  Biggs,  Cal 115 


,..  wj  TFig.  1,  Manner  of  spraying  trees  on  one  side.  Biggs,  Cal \ 

'  iFig.  2,  Action  of  curl  on  trees  sprayed  on  one  side,  B>iggs,  Cal ' 


9'> 


XVII.  Condition  of  trees  sprayed  on  one  side  at  maturity  of  fruit 124 

XYIII.   Fruit  gathered  from  sprayed  and  unsprayed  halves  of  tive 124 

XIX.  Showing  fruitfulness  of  sprayed  half  of  tree 124 

XX.  Sprayed  and  unsprayed  Crawfords  Late  trees,  Livi-  Oak,  C<i\ 142 

XXI.  Steam  spray -cooking  appliances  for  small  orchards. 158 

XXII.  Steam  spray-cooking  appliances  for  large  orchard.s 101 

XXIII.  Appearance  of  orchard  at  close  of  spray  work,  Biggs,  ('al 176 

XXIV.  Unpruned  trees,  too  late  for  spraying 1 76 

XXV.   An  orchard  properly  pruned,  but  too  late  for  si)raying 17(5 

XXVI.   An  outfit  for  spraying  small  orchards -  -  -  204 

XXVIl.  An  outfit  for  spraying  medium-sized  orcliards 204 

XXVIII.  Spraying  eight  trees  at  a  time,  Rio  Bonito  orchard,  F.iggs,  Cal 204 

XXIX.  A  power  sprayer  in  use  at  Santa  Barl )ara,  Cal 204 

XXX.  A  power  sprayer,  San  Diego,  Cal 204 


FIGURES. 


Fu;.     1.  Cyclone  nozzle,  with  direct  discharge  and  dcgorgcr 168 

2.  Cyclone  nozzle,  with  lateral  discharge,  for  thin  sprays 168 

3.  Heavy  cyclone  nozzle,  with  oblique  discharge,  for  thick  st)rays 168 

4.  Wire-extended  suction  hose 109 

5.  Bamboo  extension  pipe 109 

6.  Spray  pump  for  use  on  barrel  or  tank 171 

7.  Spray  pump  for  use  on  barrel  or  tank , 1 72 

8.  Spray  pump  for  general  orchard  work,  upright  lever 173 

9.  Spray  pumi)  for  general  orchard  work,  upright  lever 174 

10.  Pneumatic  pump  for  general  spraying 1 75 


DESCRIPTION  OF  PLATE  I. 

Cnrl-infe-«ted  peach  s^hoot  from  Biggs,  Cal.  Leaves  of  this  character  are  badly 
infested  with  Exoascus  deformans.  The  greatly  broadened  and  distorted  leaves,  which 
are  characteristic  of  this  disease,  are  shown,  and  the  whitened,  spore-covered  surface 
of.  some  of  the  more  elevated  portions  of  the  upper  surface  may  be  distinguished. 
The  petioles  of  the  affected  leaves  are  greatly  enlarged,  the  branch  is  much  bent  and 
distorted,  and  the  internodes  of  the  diseased  portion  of  the  branch  are  greatly 
shortened.  A  branch  thus  badly  diseased  is  apt  to  die  during  the  year  unless  con- 
tlitions  for  growth  are  very  favoral)le.  It  is  in  shoots  of  this  character  that  the 
mycelium  occurs  in  greatest  abundance,  but  the  hyphfe  have  been  seen  to  spread 
only  a  short  distance  beyond  the  parts  showing  the  hypertrophy.  (Compare  with 
Pis.'  V  and  VI.) 


PEACH  LEAF  CURL:  ITS  NATURE  AND 
TREATMENT. 


By  Newton  B.  Pierck. 


CHAPTER  I. 

PRIMARY     CONSIDERATIONS    RELATIVE    TO    PEACH    LEAF    CURL. 

INTRODUCTION. 

This  bulletin  has  been  prepared  to  place  before  the  peach  growers 
of  the  United  States  the  results  of  experiments  conducted  during-  sev- 
eral years  past  for  the  prevention  of  peach  leaf  curl.  The  losses 
arising  from  this  disease  frequently  amount  to  several  millions  of  dol- 
lars annuall}^  and  it  is  believed  that  a  wide  dissemination  of  the  results 
obtained  b}'  the  experiments  here  outlined  will  lead  to  a  large  .saving 
to  the  peach  industry.  During  the  progress  of  the  Department's  work 
over  one  thousand  six  hundred  peach  growers  in  all  peach-growing 
States  have  been  requested  to  test  the  preventive  measures  here  rec- 
ommended. A  large  number  have  done  so,  and  some  of  the  more 
important  results  of  their  work  are  also  given.  From  conservative 
data  it  has  been  estimated  that  the  experimental  work  thus  widely  set 
on  foot  by  the  Department  has  saved  to  the  country  in  a  single  year 
the  sum  of  three-fourths  of  a  million  dollars.  This  is  but  a  fraction, 
however,  of  what  may  easily  be  saved  in  the  future,  when  all  growers 
have  obtained  a  more  thorough  understanding  of  the  disease  and  its 
prevention. 

The  obscure  views  held  by  many  growers  in  the  past  upon  the  true 
nature  of  peach  leaf  curl,  and  the  total  lack  of  preventive  measures 
up  to  a  recent  date,  make  it  desirable  to  thoroughlj^  consider  the  sub- 
ject at  this  time  and  to  record  the  detailed  work  upon  which  the  con- 
clusions reached  are  based.  These  conclusions  are  that  peach  leaf  curl 
maybe  prevented  with  an  ease,  certainty,  and  cheapness  rarely  attained 
in  the  treatment  of  any  serious  disease  of  plants,  and  that  there  is  no 
longer  a  necessity  for  the  losses  annually  sustained  from  it  in  the 

United  States. 

11 
fltOnRTT  LlBURr 

W.  C.  State  C«lfc|« 


12  PEACH    LEAF    CUKL:    ITS    NATURE    AND    TREATMENT. 

GENERAL   CHARACTERISTICS   OF   THE    DISEASE. 

The  disease  of  peach  trees  here  considered  is  variouslj^  known  in 
diflE'erent  regions  and  languages.  In  the  United  States  it  is  commonl^v 
know  as  peach  leaf  curl,  or  curl  leaf  of  the  peach;  in  England  and 
all  British  possessions,  as  leaf  blister,  leaf  curl,  or  curly  leaf;  in 
France,  as  doque  du  pecher;  in  Germany,  as  Krauselkrankheit;  in 
itah^,  as  Fillorissema,  etc. 

Peach  leaf  curl  is  a  disease  which  seriously  aflfects  the  leaves,  flowers, 
tender  shoots,  and  fruit  of  the  peach.  Its  action  is  most  severe  in  the 
spring  of  the  3'ear,  shortly  after  the  leafing  of  the  trees,  and  the  greatest 
injuries  are  caused  in  wet  seasons  and  in  humid  localities.  The  leaves 
become  enlarged,  thickened,  much  curled,  and  distorted.  As  the  dis- 
ease progresses  the  healthful  green  of  the  foliage  is  changed  to  a  yel- 
lowish, sickly  appearance.  The  leaves  soon  fall,  and  the  newh'  formed 
fruit  ceases  to  grow,  yellows,  wilts,  and  likewise  falls.  The  total  loss 
of  foliage  and  crop  is  common  in  seasons  favorable  to  the  disease.  A 
second  growth  of  leaves  develops  more  or  less  rapidly,  according  to 
the  severity  of  the  disease  and  the  favora])le  or  unfavorable  soil  and 
atmospheric  conditions  prevailing  at  the  time.  If  the  soil  and  atmos- 
phere are  drv  and  the  temperature  high,  new  foliage  may  appear  slowly 
and  much  of  the  terminal  growth  may  die  throughout  the  orchard.  In 
severe  attacks  young  trees  are  frequentl}^  killed.  The  second  crop  of 
leaves,  appearing  on  affected  trees  after  the  spring  defoliation,  u.simlh' 
remains  comparatively  free  from  curl  for  the  rest  of  the  season.  The 
amount  of  disease  which  will  appear  upon  this  later  crop  of  foliage 
depends  largel}^  upon  the  humidity  or  dryness  of  the  atmosphere, 
excessive  moisture  fuAoring  a  contiiuiance  of  the  trouble.  The  action 
of  the  disease  .upon  spring  branches  causes  them  to  enlarge,  become 
curved  and  distorted  in  various  ways,  and  often  to  dry  up  and  die: 

GEOGRAPHIC  DISTRIBUTION. 

Peach  leaf  curl  exists  in  most  peach-growing  countries.  Its  distri- 
bution in  the  United  States  extends  from  the  Gulf  of  Mexico  to  Can- 
ada and  from  the  Atlantic  to  the  Pacific.  The  centers  of  greatest 
prevalence,  and  where  the  greatest  losses  are  sustained  from  this  cause, 
are  in  the  leading  peach-growing  districts  bordering  the  Great  Lakes, 
especially  in  Michigan  and  western  New  York;  in  the  central,  north- 
ern, and  coast  regions  of  California;  and  west  of  the  Cascade  Moun- 
tains in  Oregon  and  Washington.  The  disease  is  less  serious,  or  is  of 
minor  importance,  in  those  peach-growing  counties  of  New  York 
most  distant  from  the  lakes,  in  Pennsylvania,  Ohio,  Indiana,  Illinois, 
and  in  southern  California.  Still  less  injury  is  reported  from  New 
Jersey,  Delaware,  Connecticut,  Rhode  Island,  Massachusetts,  Mary- 


GEOGRAPHIC    DISTRIHUTION.  Hi 

land,  Viri^inia.  West  Viro-inia,  Kentiu-kv,  Tcnnossoo,  North  Carolina 
South  Carolina,  Arkansas,  Oklahoma,  Louisiana,  Mississippi,  Ahi- 
bama,  and  Florida,  l)ut  in  most  of  these  rej^ions  occasional  serious 
outbreaks  are  reported  in  seasons  favorable  to  curl  or  in  particuhir 
localities.  It  prevails  rather  more  seriously  in  portions  of  Geor- 
gia, Kansas,  and  Missouri.  In  Texas,  Now  Mexico,  Arizona,  and 
Colorado  it  has  occasioned  but  little  loss  and  is  not  widely  known. 
Reports  from  Utah  and  Nevada  are  meager,  ])ut  it  is  probal)le  that  the 
disease  prevails  to  a  limited  extent  in  both  States,  The  more  northern 
States  not  mentioned  here  have  either  failed  to  report  the  prevalence  of 
the  disease  or  are  properly  included  within  that  portion  of  the  United 
States  unsuited,  by  rigor  of  climate,  to  successful  peach  culture. 

In  Canada  ])oth  Ontario  and  British  Colum))ia,  which  are  the  leading 
peach-growing  provinces,  arc  favoral)l3^  situated  for  the  serious  devel- 
opment of  peach  leaf  curl  in  wet  seasons.  Mr.  »John  Craig,  horticul- 
turist of  the  Central  Experimental  Farm,  Ottawa,  writes  that  the 
disease  "obtains  in  Canada  in  all  the  peach-growing  disti'icts,  includ^ig 
British  Columlua  and  the  Province  of  Nova  Scotia."  It  is  known  to 
cause  considerable  losses  of  fruit  in  some  sections.* 

Peach  leaf  curl  exists  also  in  some  if  not  all  the  peach-growing  coun- 
tries of  South  America.  In  Chile  the  peach  is  wideh'  grown,  l)eing 
planted  from  the  snow  line  of  the  Andes  to  the  Pacific  Ocean,  and  from 
Copiapo  south  as  far  as  Valdivia,  a  distance  of  800  miles.  IVIr.  C.  T. 
Ward,  Jr.,'  of  the  Hacienda  Loreto,  Department  of  Limache,  says  that 
the  parasite  of  peach  leaf  curl  ''exists  all  over  the  country  where  the 
peach  grows,"  but  that  no  satisfactory  method  of  control  is  yet 
practiced  there. 

In  EuroipeDr.  R.  Sadebeck''  records  the  disease  from  Denmark,  Ger- 
many, Austria,  Switzerland,  and  Italy.  He  states  that  in  central  Ger- 
many it  prevails  more  extensively  than  in  the  vicinity  of  IIam])urg.* 
Among   the  many    German   scientists  who   have  written   upon   this 

'  Mr.  L.  Woolverton,  secretary  of  the  Fruit  Growers'  Association  of  Ontario,  said, 
in  1890,  in  a  paper  entitled,  Points  on  Peach  Growing  in  the  Niagara  District,  puli- 
lished  in  tlie  Annual  Report  of  tlie  Society  for  that  year,  pp.  5(5  and  57:  "  Tlie  peach 
has  its  share  of  enemies  and  diseases,  cliief  among  which  are  the  curl,  curcnlio,  the 
borer,  and  the  yellows.  For  the  curl  I  know  no  remedy.  It  is  not  often  severe,  hut 
sometimes  with  the  diseased  leaves  the  fruit  also  drops."  Mr.  John  Craig,  in  writing 
from  Ottawa  under  date  of  October  7,  1897,  says,  relative  to  tiie  di.'jease  in  Ontario: 
"  It  is  only  severely  injurious  here  during  years  of  unusually  heavy  rainfall.  This 
year  it  was  very  load." 

2  Letter  of  March  22,  1896,  to  IVIr.  J.  M.  Dobbs,  U.  S.  Consul  at  Valparaiso,  Cliile. 

^Sadebeck,  Dr.  R.,  Die  parasitischen  Exoasceen.  Fine  Monographic,  IIaml)urg, 
189;^,  !>.  94. 

*Satlebeck,  Dr.  IL,  Untersucli.  ul)crdie  I'ilzgattung  Kxoascus,  liaml mrg,  1SS4,  p. 
115. 


14         PEACH  lp:af  curl:  its  nature  and  treatment. 

disease  and  its  cause  are  Sadebeck,^  Winter,'  De  Bary,^  von  Tavel,* 
Ha  tig/  Zopf,''  Tubeuf/  Ludwig,*  Sorauer,'  Frank/«  Kirchner," 
Fuckel/"  and  others.  Winter  says  (1.  c.)  that  the  fungus  of  this 
malady  causes  great  damage  by  early  defoliation  of  the  trees,  and  that 
it  even  kills  the  diseased  trees  by  its  repeated  occurrence. 

In  Great  Britain  peach  leaf  curl  has  been  common  for  a  great  many 
years.  In  1821  it  was  accurately  described  by  an  English  gardener 
under  the  name  of  "'blight."  He  says:''*  "Under  this  denomination 
[l)light]  are  frequently  confounded  two  varieties  of  disease  materially 
different  in  their  appeanince,  and  which  I  shall  distinguish  by  the 
appellation  of  hlister  and  curl.  The  former  is  generally  confined  to 
such  peach  trees  as  have  glandular  leaves,  which  are  mostly  subject 
to  it  in  the  months  of  April  and  May,  and  when  attacked  it  is  not 
until  the  latter  part  of  the  season,  if  at  all,  that  they  become  healthy. 
The  leaves  so  attacked  are  crisp,  and  assume  a  swollen,  crumpled,  and 
succulent  appearance;  the  shoots  themselves  are  affected  by  it  in  the 
saipe  manner,  and  never  produce  either  good  blossom  or  healthy  wood." 
Berkele}^ "  has  described  the  fungus  causing  this  disease,  and  it  has 
been  mentioned  by  Bennett  and  Murray  ^''  and  many  other  English 
writers.  (Consult  a  popular  article  on  Peach  Blister,  by  W.  G.  Smith, 
Gardeners'  Chrmide.,  Vol.  IV,  pp.  36,  37.) 

^Sadebeck,  Dr.  E.,  see  locations  cited;  also  Einige  neue  Beobachtungen  und  krit- 
ische  Benierkungen  liber  die  Exoascacepe,  Bot.  Ges.,  1895,  Band  XIII,  Heft  fi. 

^Winter,  Dr.  Georg,  Die  durch  Pilze  verursachten  Krankheiten  der  Kulturge- 
wiichse,  Leipzig,  1878,  p.  47;  also  Rab.  Kryjjt.  Flora,  1885,  II,  p.  6. 

^De  Bary,  Prof.  A.,  Comparative  Morphology  and  Biology  of  the, Fungi,  ^lyceto- 
zoa,  and  Bacteria,  English  edition,  Oxford,  1887,  p.  265;  see  also  in  the  same  volmne 
various  other  references  to  the  arrangement  and  position  of  the  Exoascus  group. 

*  Tavel,  Dr.  F.  von,  Vergleichende  Morphologie  der  Pilze,  Jena,  1892,  ^-p.  55, 56. 

^Hartig,  Dr.  Robert,  Lehrbuch  der  Baumkrankheiten,  Berlin,  1889,  p.  118;  also 
the  English  edition,  Text-book  of  the  Diseases  of  Trees,  London,  189-1,  p.  132. 

''Zopf,  Dr.  Wilhelm,  Die  Pilze  in  morphologischer,  physiologischer,  })iologischer, 
und  systematischer  Beziehung,  Breslau,  1890,  pp.  236,  282. 

'Tubeuf,  Dr.  Karl  Freiheer  von,  Pflanzenkrankheiten  durch  kryptogame  Para- 
siten  verursacht,  Berlin,  1895,  pp.  167-188. 

*Ludwig,  Dr.  Friedrich,  Lehrbuch  der  Niedereu  Kryptogamen,  Stuttgart,  1892, 
p.  205. 

^Sorauer,  Dr.  Paul,  Handbuch  der  Pflanzenkrankheiten,  Zweiter  Theil,  Die  para- 
sitilren  Krankheiten,  Berlin,  1886,  p.  278. 

1° Frank,  Dr.  A.  B.,  Die  Krankheiten  der  Pflauzen,  Band  II,  Die  Pilzparasitilren 
Krankheiten,  Breslau,  1896,  pp.  249,250.     Edition  of  1880-81,  Vol.  II,  p.  526. 

'^Kirchner,  Dr.  Oskar,  Die  Krankheiten  und  Beschiidigungen  unserer  landwirt- 
schaftlichen  Kulturpflanzen,  Stuttgart,  1890,  pp.  324, 407. 

'^  Fuckel,  L.,  Symbolte  mycologicse,  1869,  p.  252. 

'^  See  quotation  in  Report  of  Michigan  Pomological  Society  for  1873,  pp.  16,  17. 

'* Berkeley,  M.  J.,  Introduction  to  Cryptogamic  Botany,  1857,  p.  284,  and  Outlines 
of  British  Fungology,  London,  1860,  pp.  376,  444,  tab.  1,  fig.  6. 

'^Bennett,  A.  W.,  and  Murray,  George,  A  Handbook  of  Cryptogamic  Botany, 
London,  1889,  p.  379. 


GEOGRArHlC    DISTRIBUTION.  15 

Tulasne/  Prillicnix,"  iiiul  others  (Coins  coinplcto  (rajrriculturc,  T. 
XV,  p.  255,  art.  IYh-Ium-)  have  studied  this  disease  more  or.  less  care- 
fully iu  France,  where  it  often  develops  in  a  scM'ious  form.  In  June, 
181>0,  the  writer  saw  the  peach  trees  near  th(>  Mediterranean,  particu- 
larly about  Montpellier,  in  anything  but  a  healthy  condition.  On  the 
Hd  of  June  leaf  curl  was  l)ad,  and  the  ends  of  ])ranches  were  seen  to 
he  dying-  in  some  cases.  In  Italy  Briosi  and  Cavara,-'  Berlese/  and 
Comes  ^  are  among  those  who  have  described  this  malady.  The  dis- 
ease varies  in  its  prevalence  through  Italy  in  accordance  with  its 
habits  elsewhere.  The  trees  of  northern  Italy  appeared  more  iiealth- 
ful  than  in  the  south  of  France  during  the  \isit  of  the  Avriter  in  18tM), 
but  considerable  gummosis,  perhaps  due  to  the  same  cause,  was 
observed  in  both  regions.  In  western  Sicily,  near  Palermo,  leaf  curl 
was  again  encountered  in  severe  form.  The  situation  in  Spain  and 
Portugal  is  not  known,  but  in  the  more  humid  coast  regions  it  should 
not  be  materially  different  from  the  condition  found  in  Itah\  In 
Greece,  as  stated  })y  Prof.  P.  Genardius,''  the  disease  rarely  causea. 
any  damage  of  importance,  ])ecause  of  the  dryness  of  the  climate,  and 
for  this  reason,  he  states,  no  treatment  has  becMi  tried.  In  Austria- 
Hungarj^  the  situation  respecting  leaf  curl  is  nuich  the  same  as  in 
Italy.  Dr.  Johann  Bolle,  director  of  the  Institute  of  Experimental 
Agricultural  Chemistry,  at  Gorizia,  writing  from  the  island  of  Cherso, 
under  date  of  Octol)er  25,  1897,  states  that  in  rainy  weather 
the  disease  appears  some  years  with  great  intensity  and  causes  great 
damage.  In  Roumania  the  situation  is  much  the  same.  Prof.  Wilhelm 
Knechtel,  of  the  Agricultural  School  of  Herestrau,  states  in  a  letter 
dated  Bucha.rest,  October  IT,  1897,  that  in  that  country  leaf  curl  of  the 
peach  is  also  a  troublesome  and  destructive  disease  to  which  the  trees 
are  subject  in  many  years.  He  states  that  Roumania  has  in  the  region 
of  the  lower  Danube  almost  a  steppe  climate — in  sunuuer  very  hot 
and  dr}',  in  winter  cold,  with  very  abrupt  temperature  changes,  so 
that  the  variations  of  temperature  within  twenty-four  hours  not  infre- 
quently amount  to  from  10°  to  15°  R.  (22.50°  to  33.75°  F.).  When 
such  changes  of  temperature  occur  in  the  spring  at  the  time  of  leaf 
development  the  disease  is  certain  to  appear.  The  growth  of  the 
\'egetation,  which  has  been  favored  through  the  preceding  warm  days, 
is  checked  during    succeeding  days  of  lowered  temperature,   when 

'Tulasne,  L.  R.,  Ann.  d.  Sci.  Nat.,  1866,  ser.  5,  T.  V,  p.  128. 

■'  Prillieux,  Ed.,  Bull,  de  la  Soc.  Bot.  de  France,  1872,  T.  XIX,  pp.  227-2.30;  Compt. 
Rend,  li;  also  Maladies  des  Mantes  Agricoles,  Paris,  189.5,  T.  I,  pp.  894-400. 

^Briosi,  G.,  and  Cavara,  F.,  Fungi  Parassiti  d.  Piante  Coltiv.  od  Utili,  essice.,  delin. 
e  descr.,  1891,  fasc.  5,  No.  104. 

^Berlese,  A.  N.,  I  Parassiti  Vegetali  d.  I'ianto  Coltiv.  <>  I'tili.  Milano,  189.5,  ])p. 
124-126. 

"Comes,  O.,  Crittoganiia  Agraria,  NajMjli,  1891,  i)p.  Ui'-i,  165-167,  549. 

"Letter  dated  Athens,  Sept.  12,  1895. 


16  PEACH    LEAF    CUKL*.    IT8    NATl'KE    AND    TREATMENT. 

the  development  of  the  fungus  ])egin.s,  .so  that  in  June  all  leaves  at  the 
ends  of  the  young  l)ranchos  are  curled  and  deformed  and  perhaps  all 
the  blossom  ])uds  fall  oH'.  If  the  more  developed  leaves  at  the  base  of 
the  young  shoots  prove  more  resistant  to  the  fungous  action,  then  fresh 
shoots  are  formed  in  June,  even  if  not  in  normal  condition,  but  yet 
somewhat  healthy,  so  that  the  tree  remains  intact.  Tn  the  more  pro- 
tected hill  regions  of  the  vineyards,  at  the  foothills  of  the  Carpathian 
Mountains,  this  disease  is  also  troublesome,  but  less  intense  tlian  in 
other  parts  of  the  country. 

Peach  leaf  curl  exists  in  South  Africa,  and  prolmbly  also  throughout 
Algeria  and  other  peach-growing  portions  of  the  continent.  Professor 
MacOwan,  of  the  department  of  agriculture  of  Cape  Colony,  has 
written  of  the  disease  in  South  Africa,  giving  his  views  as  to  the 
j)roper  manner  of  treating  the  same. ^  He  also  writes  that  it  is  "a 
great  plague  at  the  Cape."'" 

A  peach  grower  of  Drysdale,  Frere,  Natal,  in  writing  to  the  C'ape 
Colony  agricultural  department  under  date  of  October  81,  1S98,  says 
that  he  has  a  good  many  peach  trees  of  the  yellow,  white,  and  St. 
Helena  varieties,  and  that  they  are  all  affected  with  the  discolored  and 
curled-up  leaves  characteristic  of  this  disease;  that  several  of  his  neigh- 
bors are  complaining  that  their  peach  trees  are  suffering  like  his;  and 
that  the  disease  seems  to  be  spreading.  The  young  trees  were  simi- 
larlv  affected.  ^ 

Perhaps  no  foreign  country  has  suffered  more  from  peach  leaf  curl 
than  New  Zealand.  Mr.  W.  M.  Maskell,  of  Wellington,  writes  as 
follows  :  *  "  The  curly  l)light  has  ])een  for  many  years  prevalent  in  this 
country — so  much  so  that  whereas  in  the  earh'  days  peaches  were  exi-eed- 
ingly  luxuriant  and  fine,  they  have  dwindled  to  comparativel}^  very 
small  and  poor  trees  and  in  many  parts  of  the  colony  almost  died  out. 
In  the  last  two  or  three  years  the  people  have  been  advised  to  emploj'' 
remedies,  and  have  done  so  to  some  extent,  so  that  there  is  a  marked 
improvement  in  the  peach  orchards.  *  *  '^''  I  can  myself  recollect, 
early  in  the  sixties,  when  the  most  splendid  peaches  used  to  gi-ow 
wild  in  the  warm  northern  districts,  where  now  scarcely  a  tree  is 
seen;  and  the  curly  blighthas  been  a  dreadful  curse  all  over  the  colon}'." 

Australians  report  peach  leaf  curl  among  their  serious  plant  dis- 
eases. In  South  Australia  it  ""has  been  known  quite  twent}-  3^ears,'"' 
and  probably  longer,  and  occasions  considerable  losses  in  seasons 
favoring  it.     The  situation  is  much  the  same  in  New  South  Wales. 

'  MacOwan,    Prof.    P.,  Agricultural  Journal,    published    by  the    department    of 
agriculture  of  Cape  Colony,  1892,  Vol.  V,  pp.  252,  253. 
.    -Letterdated  Cape  Town,  Oct.  26,  1895. 

•■'Agricultural  Journal,  Cape  Colmiy,  Vol.  YI,  No.  23,  p.  451. 

•*  Letter  dated  Wellington,  New  Zealand,  Deceml)er24,  1895. 

^Observations  of  ]\Ir.  A.  Molineux,  general  secretary  for  the  agricultural  hurcau 
of  South  Australia,  letter  dated  Adelaide,  February  11,  1895. 


GEOGRAPHIC    DISTRIBUTION.  17 

Prof.  N.  A.  Co])l),'  i){ithologist  for  the  agriculturiil  department  of  that 
colony,  bus  deserilxHl  the  malady  (^uite  fully,  and  althouj^h  he  fails  to 
specify  particular  localities,  it  is  pro))al)le  that  his  descriptions  arc 
drawn  from  observations  made  in  the  colony  for  which  he  writes.  He 
says  that  in  the  most  severe  eases  of  the  disease  '"  the  fruit  falls  about 
three  weeks  after  setting,  and  not  a  peach  is  h'ft  to  ripen.  This  oeeurs 
on  trees  on  which  the  disease  is  chronic  and  severe.  *  *  *  Such 
trees  are  worthless,  nay,  worse  than  worthless;  they  are  a  constant 
menace  to  the  peacli  trees  in  the  neigh))orhood.  The  sooner  they  are 
cut  down  and  burned,  and  thus  utterly  destroyed,  the  better  it  will  be 
for  the  peaeh  industry.  "■  "■  ■"  I  have  now  describedthe  disease  in 
its  worst  form,  a  form  in  which  it  is  not  common.  The  milder  forms 
of  the  disease  are  much  more  frequent." 

Peach  leaf  curl  also  prevails  in  Victoria,  where  it  has  ])een  placed,- 
according  to  Mr.  D.  McAlpine,'  pathologist  for  Victoria,  among  the 
specified  diseases  in  the  vegetable  diseases  bill,  recently  passed  in  that 
colon^^  ]\Ir.  ]\Ic  Alpine  also  says  that  according  to  Mr.  George  Neilson, 
chief  inspector  luider  the  vegetation  diseases  act,  it  has  been  known 
in  Victoria  since  1856,  and  affected  peach  trees  were  just  as  bad 
then  as  now.  INlr.  ]\IcAlpine  adds:  "The  disease  is  distributed  all 
over  the  colony.  In  the  cooler  districts  it  is  generally  more  severe 
than  in  the  northern  and  warmer  districts,  and  it  is  generally  more 
prevalent  in  a  moist  and  cool  spring  than  in  a  dry,  warm  one." 

The  situation  in  Japan  has  been  learned  through  the  obliging  and 
careful  inquiries  of  Prof.  K.  Miyabe,^  of  the  Sapporo  Agricultural 
College.  He  writes  that  Exoascas  deformans  is  at  present  a  serious 
pest  to  the  peach  trees  at  Sapporo,  north  island,  and  states  that  his 
attention  was  first  called  to  its  presence  in  that  place  some  three  or 
four  years  since,  but  that  there  is  no  doubt  of  its  existence  from  the 
time  of  the  first  introduction  of  American  peach  trees,  about  twenty- 
three  years  ago.  The  Japanese  flowering  (double  red)  peach  trees  and 
nectarines  were  introduced  at  Sapporo  by  a  florist  about  six  or  seven 
years  ago  from  Echigo  Province  in  the  northern  part  of  the  main 
island  or  Honsiu.  These  varieties  were  found  to  be  attacked  to  some 
extent  during  these  few  years.  American  varieties  are  now  most  seriouslj'^ 
affected,  and  man}'  persons  have  been  obliged  to  cut  down  their  trees 
on  account  of  the  disease.  Respecting  the  distribution  throughout 
Japan,  Professor  Miyabe  says:  "As  to  the  rest  of  Hokkaido  [the 
northern  island]  I  found  the  fungus  in  1890  at  Mombetsu,  a  farming 
village  on  Volcano  Bay,  settled  about  twenty-seven  years  ago  by  the 
people  from  Sendai.  I  could  not  tell  whether  the  pe^ach  trees  culti- 
vated there  were  of  American  or  Japanese  origin.     In  Honsiu,  or 

^Cobb,  Prof.  N.  A.,  paper  in  the  Agricultural  Gazette,  1892,  Vol.  Ill,  pp.  1001-1004. 
■''Letters  dated  Melbourne,  Australia,  July  14,  1896,  and  Oct.  12,  1897. 
*  Letter  dated  Sapporo,  Hokkaido,  Japan,  Nov.  22,  1897. 
19093— No.  20 2 


18  PEACH    LEAF    CUKL*.    ITS    NATURE    AND    TREATMENT. 

Main  Ishmd,  the  peach  curl  seems  to  be  prevalent  only  in  the  northern 
provinces.  *  *  *  I  sent  letters  of  in(iuiry  relating-  to  this  (Question 
to  the  graduates  of  our  college,  who  studied  especially  al)out  the 
parasitic  fungi  in  our  laljoratory,  and  whose  opinions  I  can  trust. 
From  ]Mr.  Y.  Tukahashi,  at  Morioka,  in  Rikuchu  Province,  I  received 
the  following  an.swer  :  'Peach  curl  is  very  prevalent  in  this  town. 
Almost  every  tree  is  more  or  less  attacked  by  the  fungus.  I  saw  some 
trees  entirely  attacked.  At  the  end  of  summer  [spring?]  all  the  dis- 
eased leaves  fell  to  the  ground  and  new  leaves  were  produced.'''  In 
the  southern  island,  Kumamoto,  a  correspondent  reported  to  Professor 
Mij^abe  that  the  disease  had  not  been  seen  there  by  him.  From  Tokyo 
Professor  Shirai,  of  the  College  of  Agriculture,  reports  that  he  has 
not  yet  found  the  disease  in  that  section  of  the  main  island. 

In  China,  as  the  writer  is  informed,  peach  leaf  curl  prevails  to  a 
very  large  extent,  and  the  losses  are  probalily  considerable  from  this 
cause.  ^ 

ORIGIN    OF   THE    DISEASE. 

The  country  of  origin  of  peach  leaf  curl  is  not  positively  known. 
It  was  hoped  that  the  inquiry  as  to  distribution  would  develop  posi- 
tive information  respecting  this  point,  but  such  has  not  been  the  case. 
That  seedling  peaches  are  remarkably  susceptible  to  the  disease,  and 
that  the  Chinese  Saucer  peach  is  among  those  most  subject  to  it, 
appears  to  indicate  that  the  home  of  the  peach  is  the  source  of  the 
disease,  and  that  the  two  may  have  come  to  us  together  from  a  com- 
mon point  of  origin.  Recent  studies  have  been  constantly  tending 
to  reduce  the  number  of  species  of  plants  once  thought  to  be  subject 
to  curl.  At  present  it  is  believed  that  it  is  confined  almost  wholly  to 
the  peach  or  its  derivatives,  as  the  nectarine  and  peach-almond.  The 
exceptions  to  this,  where  the  disease  has  been  noted  on  the  plum, 
almond,  etc.,  are  rare,  and  not  sufficiently  numerous  or  general  to  mate- 
rially affect  the  evidence  that  the  peach  is  the  natural  host  of  the  fungus. 
Thus  far,  however,  it  has  been  impossible  to  learn  if  the  peach  in  the 
interior  of  China,  its  supposed  home,  is  affected  by  this  trouble,  though 
in  the  coast  regions  it  is  said  to  prevail  extensively.  Such  information 
as  has  been  obtained  from  Japan  indicates  the  recent  introduction  of 
the  disease  in  that  country,  and  that  the  United  States  is  probably  its 
source  rather  than  the  near-by  continental  coast.  I'n  Australia,  how- 
ever, this  may  properly  be  questioned,  for,  as  already  mentioned,  Mr. 

^  Letter  from  Augustus  White,  Esq.,  forwarded  April  3,  1896,  through  the  kindness 
of  Mr.  Eufus  S.  Eastlack,  then  U.  S.  Deputy  Consul-General  at  Shanghai,  China. 
Mr.  White  says,  in  conckiding  his  statements,  that  the  Chinese,  ignorant  of  the  use 
of  the  knife  in  pruning,  trust  solely  to  an  annual  inspection  of  the  trees  at  the  time 
the  blossoms  set,  when  they  carefully  pick  off  all  excess  of  fruit,  and  with  it  all 
diseased  leaves,  etc.,  but  allow  these  to  fall  to  the  ground  and  remain  under  the 
trees  to  rot  or  reproduce  the  plague,  as  nature  thinks  best. 


LOSSES    FROM    TIIK    DISK  ASK.  19 

Gcorg'O  Nc'ilsoii,  chict"  inspector  iiiulcr  tlif  \'co-cttitioii  diseases  act  of 
that  colony,  states  that  ju^ach  h'af  curl  has  hiMMi  known  in  Victoria  since 
185t).  This  dates  thi>  })resence  of  the  disease  in  Australia  hack  to  a 
time  when  its  inn)ortation  from  Amei'ica  to  that  country  would  he 
douhtful.     Its  FiUro])ean  origin,  however,  may  not  he  im|)i-()hal>lc. 

The  severity  of  the  disease  in  the  gardens  of  C'iiina  and  the  fact  that 
the  peach  probably  reached  Europe  and  America  fiom  the  East  make 
it  still  desirable  to  learn  if  the  trouble  is  ])revalent  amono-  the  wild  or 
escaped  peach  trees  in  the  intcMior  of  the  Chinese  Kmpir(\ 

It  may  be  pertinent  to  state,  in  view  of  the  fact  that  Dai'win  holds 
the  peach  to  be  derivcnl  from  the  almond,  that  none  of  the  many  widely 
cultivated  varieties  of  the  almond  in  California,  either  of  local  or  for- 
eign origin,  arc  subject  to  peach  leaf  curl,  even  wIkmi  growing  beside 
peach  orchards  denuded  by  it.  Trees  which  are  api)arently  the  result 
of  almond  and  peach  crosses  are  somewhat  ati'ected,  however,  and  sev- 
eral of  the  nectarines,  which  are  derived  from  the  peach,  are  quite 
subject  to  it.  Seedling  peacht\s,  as  stated,  arc  very  commonly  attacked, 
but  of  some  forty  to  tift}^  varieties  of  seedling  almonds  examined  by 
the  writer  none  has  thus  far  shown  the  disease. 

LOSSES   FROM    THE    DISEASE. 

The  direct  annual  losses  to  the  peach  interests  of  the  United  States 
from  peach  leaf  curl  are  very  large,  and  arc  usually  much  greater 
than  is  suspected  by  the  growers  themselves,  as  the  nature  and  action 
of  the  disease  are  misunderstood  by  them,  and  its  effects  frequentl}'^ 
attributed  to  other  causes.  In  case  an  orchard  is  so  affected  that  it 
fails  to  hold  the  crop,  or  sets  but  a  partial  crop,  the  grower  has  but 
little  ground  for  an  opinion  as  to  what  the  jdeld  would  have  been  had 
curl  not  prevailed,  hence  the  estimates  of  losses  made  by  growers  are 
frequently  very  unsatisfactory.  In  case  curl  occurs  after  a  severe 
cold  spell  in  spring,  as  is  quite  commonly  the  case,  the  orchardist  is 
apt  to  charge  the  loss  of  fruit  to  the  low  temperature  rather  than  to 
the  disease.  The  preventive  spray  work  conducted  by  the  Depart- 
ment has  shown,  also,  that  the  loss  estimates  are  nearly  always  too 
low. 

By  preventing  the  disease  upon  a  portion  of  the  trees  of  an  orch- 
ard the  amount  of  injury  sustained  by  the  untreated  trees  has  been 
determined  most  accurately  by  direct  comparison.  Such  comparative 
work  has  now  been  conducted  for  several  years  in  many  of  the  leading 
peach-growing  centers  of  the  country,  and  these  tests  enable  the 
writer  to  state  that  the  losses  sustained  l)y  the  peach  industry  are 
probably  not  overdrawn  in  the  following  estimates:  Of  a  large  num- 
ber of  peach  growers  who  replied  to  a  circular  letter  sent  them  in 
1893,  there  were  251,  living  in  35  peach-growing  States  and  Terri- 
tories, who  stated  whether  or  not  their  orchards  were  affected  by  curl. 


20     PEACH  LEAF  CUKL:  ITS  NATUKE  AND  TREATMENT. 

'^Sixty-three  per  cent  of  -thcac  (158  growers)  reported  thtU  their 
orohiirds  were  affected,  and  37  per  cent  (93  growers)  reported  that 
their  trees  had  not  been  troubled  by  it.  Of  the  158  whose  trees 
were  affected,  60  per  cent  (104  growers),  or  about  42  per  cent  of  the 
251  orchardists  reporting  on  this  disease,  reported  more  or  less  loss. 
The  growers  who  reported  loss  were  residents  of  21  States,  and  were 
scattered  from  the  Atlantic  to  the  Pacific.  The  losses  sustained  varied 
from  a  small  amount  of  fruit  to  the  entire  crop,  and  in  some  instances 
many  of  the  young  trees  were  killed.  Of  the  entire  number  of  reports 
received  as  to  the  presence  or  absence  of  curl  in  the  orchard  of  the 
grower,  93  came  from  States  or  sections  of  the  country  where  little 
leaf  curl  prevails,  as  Texas,  Delaware,  Florida,  Kansas,  etc.,  so  that 
the  data  should  be  strictly  representative  of  the  peach-growing  coun- 
try as  a  whole.  The-  replies  received  were  from  Alabama,  Arizona, 
Arkansas,  California,  Colorado,  Connecticut,  Delaware,  Florida,  Geor- 
gia, Idaho,  Illinois,  Indiana,  Kansas,  Kentucky,  Louisiana,  Maryland, 
Massachusetts,  Michigan,  Mississippi,  Missouri,  Nebraska,  New  Jer- 
sey, New  Mexico,  New  York,  North  Carolina,  Tennessee,  Texas, 
Virginia,  Washington,  and  West  Virginia. 

The  amount  of  loss  sustained  by  the  42  per  cent  of  the  growers 
reporting  losses  is  given  in  the  replies  in  various  ways.  Some 
growers  have  reduced  their  loss  to  dollars  and  cents;  others  have  indi- 
cated the  loss  in  percentage  of  crop;  while  still  others  have  used  some 
term,  such  as  '\slight"  loss,  '\smair'  loss,  etc.,  as  a  reply  to  the 
inquiry.  In  estimating  the  true  loss  sustained  by  these  growers  a 
uniform  system  has  been  adopted.  Where  the  loss  has  been  stated  in 
dollars  the  amount  has  l^een  recorded  as  given.  Where  the  loss  is  given 
in  percentage  of  crop  the  cash  loss  has  been  determined  from  the  basis 
used  by  the  United  States  Census  Bureau  in  determining  the  ^'alue  of 
peach  crops  for  the  Eleventh  Census.  A  full  peach  crop  was  valued 
at  1150  per  acre,  and  all  portions  of  a  crop  at  the  same  rate.  Where 
the  report  of  the  grower  was  indefinite,  the  statement  being  that  the 
loss  was  small,  it  has  been  placed  at  $2.50  per  acre,  which  amounts  to 
about  2i  cents  per  tree  as  usually  planted.  It  is  probable  that  this 
is  nmch  below  the  average  loss  in  such  cases,  as  a  loss  so  small  as 
this  would  usually  escape  notice.  In  all  the  calculations  in  these  esti- 
mates an  effort  is  made  not  to  overrate  the  loss.  These  calculations 
gave  a  loss  to  the  growers  averaging  $10.95  per  acre  for  the  acreage 
reported  as  suffering  from  the  disease,  or  42  per  cent  of  the  full  area. 
This  IS  equivalent  to  about  |4.60  per  acre  for  the  entire  acreage,  or 
about  4  cents  per  tree.  At  first  thought  this  may  seem  high,  but  this 
is  more  apparent  than  real.  If  one  10-acre  orchard  loses  its  crop  from 
curl,  valued  at  $150  per  acre,  the  loss  amounts  to  $1,500.  There  may 
be  32  other  orchards  of  10  acres  each  all  al)out  this  orchard  where  not 
a  peach  is  lost,  yet  the  average  for  such  ti  district  is  the  same  as  that 
stated.     This  is  perhaps  a  clearer  manner  of  putting  the  matter  than 


LOSSES    FROM    THE    DISEASE.  21 

by  phu'iiiy;  ;iii  iivonigc  l<^ss  foi-  all  orchards.  The  loss  may  ho  viewed 
in  still  another  manner.  If  an  orchardist  has  grown  peaches  for  32 
years  and  lost  only  oni^  crop  dnrino-  that  time  from  leaf  curl  his  loss 
for  the  third  of  a  century  will  average  as  high  as  here  calculated. 

There  are  large  sections  of  the  country  where  curl  is  scarcely  known, 
as  in  portions  of  Texas.  For  such  regions  the  preceding  estimates  may 
appear  high.  On  the  other  hand,  there  are  other  prominent  sections 
of  the  country  devoted  to  peach  culture  where  these  estimated  losses 
will  certainly  ])e  far  too  low. 

If  the  preceding  calculations  and  statements  are  accepted  as  fairly 
representing  the  situation  throughout  the  country,  the  annual  losses 
fi"om  curl  in  the  United  States  may  be  approximated.  The  P^leventh 
Census  reports  the  orchards  of  peach  trees  in  the  United  States  at 
that  time  (1889-90)  as  507,736  acres,  and  from  replies  to  our  circular 
we  are  led  to  believe  that  curl  was  present  in  63  per  cent  of  these 
orchards  and  that  42  per  cent  sustained  some  loss  from  the  disease. 

Most  of  the  orchards  included  in  the  42  per  cent  sustained  only  a 
slight  loss,  but  a  very  small  percentage  sustained  a  heavy  loss,  some- 
times amounting  to  the  entire  crop.  The  average  loss  for  the  42  per 
cent  of  the  orchards  is  found  to  amount  to  $10.95  per  acre,  or  about 
10  cents  per  tree,  averaging  the  trees  at  108  per  acre.  The  total 
acreage  of  the  country  being  507,736,  the  loss  should  be  calculated 
upon  42  per  cent  of  this,  or  213,249  acres,  which  gives  a  total  esti- 
mated annual  loss  from  peach  leaf  curl  of  $2, 335. 07(5.  In  this  estimate 
no  account  has  been  taken  of  the  great  injury  to  the  growth  of  trees, 
the  injury  to  nursery  stock,  the  death  of  young  orchard  trees,  nor  the 
loss  to  succeeding  crops  from  the  reduced  ninnber  or  quality  of  fruit 
buds  on  affected  trees.  There  is  also  the  loss  arising  from  the  culti- 
vation and  pruning  of  unproductive  orchards,  which,  if  it  could  be 
determined,  would  probably  bring  the  entire  annual  loss  to  the 
country  up  to  $3,000,000  or  more. 

Since  1893,  when  the  investigation  of  this  disease  was  undertaken 
by  the  writer,  a  very  large  amount  of  correspondence  has  been  con- 
ducted with  peach  growers  in  all  parts  of  the  Union  who  have  sus- 
tained losses  from  curl,  and  this  correspondence  has  resulted  in  the 
accunuilation  of  a  large  number  of  facts  respecting  these  losses. 
These  data,  however,  have  not  been  drawn  upon  in  the  above  esti- 
mates, as  it  might  be  claimed  that  they  were  from  growers  only  who 
have  suffered  from  the  disease,  and  consequently  would  not  fairly 
represent  the  industry  as  a  whole — a  claim  which  can  not  be  made 
against  the  circular  letter,  the  basis  of  the  estimates,  which  was 
addressed  to  peach  growers  in  general  in  all  parts  of  the  United 
States.  In  fact  there  appears  to  have  been  a  larger  percentage  of 
replies  received  from  sections  of  the  country  where  curl  is  scarce 
than  from  the  more  affected  portions. 


CHAPTER  IT. 

NATURE  OF  PEACH   LEAF  CURL. 

The  study  of  the  nature  of  ])hint  diseases  is  intimately  linked  with 
the  stud}^  of  plant  physiology,  and  the  true  science  of  vegetable 
pathology  is  largely,  as  Ward  has  defined  it,  the  study  of  abnormal 
physiology.  (Introduction  to  Hartig's  Text-book  of  the  Diseases  of 
Trees.)  These  facts  become  evident  when  studying  the  etiology  of 
peach  leaf  curl  and  the  conditions  attendant  upon  its  widespread 
development.  The  direct  cause  of  peach  leaf  curl  has  long  been 
known  as  a  parasitic  fungus,  Exoascus  deformans  (Berk.)  Fuckel, 
but  it  is  evident  from  a  careful  study  of  the  disease  that  the  injurious 
development  of  the  fungus  is  distinctly  correlated  with  special  physi- 
ological phenomena  of  the  peach  tree  itself.  These  conditions  of  the 
tree  are  in  turn  dependent  upon  such  external  influences  as  tem- 
perature, the  humidity  of  the  soil  and  atmosphere,  and  others.  Such 
facts  were  foreshadowed  by  the  theories  advanced  by  peach  growers 
as  to  the  cause  of  the  disease.  Many  growers  have  considered  peach 
leaf  curl  as  the  direct  result  of  excessive  moisture  and  low  tem- 
perature or  sudden  changes,  and  as  these  physical  conditions  cer- 
tainly have  an  important  bearing  upon  the  injurious  development  of 
the  disease,  they  are  considered  together  with  the  direct  relations  of 
the  parasite  to  its  host.  However,  too  much  stress  can  not  be  placed 
upon  the  fact  that  the  fungus  alone  is  responsible  for  the  injury  to  the 
tree.  Without  the  parasite  not  a  leaf  would  curl  nor  a  peach  fall  on 
account  of  this  malady — in  fact,  no  such  disease  would  exist.  This  is 
shown  by  the  work  hereafter  detailed.  It  is  fortunate  that  the  direct 
cause  of  peach  leaf  curl  is  a  parasitic  fungus  rather  than  unfavorable 
atmospheric  conditions,  for  the  latter  could  not  be  controlled,  while 
the  control  of  the  fungus  has  been  found  practicable,  simple,  and  inex- 
pensive. 

IMIYSICAL    CONDITIONS    INFLUENCINd    THE    DISEASE. 

The  influences  of  temperature,  humidity,  situation ,  soil,  etc. ,  upon  leaf 
curl  are  often  so  well  marked  that  they  have  frequently  and  in  fact  quite 
generally  l)een  mistaken  for  the  active  cause  of  the  disease.  Indeed  a 
very  large  percentage  of  peach  growers  have  maintained,  to  within  the 
past  ten  or  fifteen  years,  that  sudden  changes  of  temperature  occurring 
in  conjunction  with  wet  weather  ari^  the  sole  cause  of  the  curling  and 
22 


PHYSICAL    CONDITIONS    INFLUENC1N(}    THE    DISEASE.  28 

loss  of  foliag-0.  Notwithstaiulino-  the  iiuihIh'i-  of  known  facts  lo  the 
contrary,  there  are  even  now  many  lirowcrs  who  rctiiin  this  i(U'ii  to  the 
utter  and  needless  loss  of  their  crops.  Th(>  wi-iter  lias  met  men  wiio  so 
firmly  believe  that  leaf  curl  is  due  to  unoontroUahh' climatic  inlhieiiccs 
that  they  would  not  consider  other  explanations.  IxMny-  unwillino- to 
visit  the  orchard,  though  the  crop  was  beinji-  lost  throitoh  curl  and 
by  so  doing-  future  crops  might  have  ))een  saved. 

To  gather  the  experience  of  peach  growers  in  general  respecting  the 
conditions  under  which  leaf  curl  develops  most  severely,  a  circular  of 
incjuiry  was  addressed  to  several  hundred  orchardists  in  November, 
18iK>.  The  replies  to  some  of  the  (juestions  are  presented.  Among 
the  iiKpiiries  the  growers  were  recjuested  to  state  if  they  iiad  o])served 
the  disease  to  be  more  prevalent  after  a  cold  spell  in  the  spring.  To 
this  (juestion  97  replies  were  received,  89  affirmative,  6  negative,  and 
2  growers  said  they  had  o])served  no  difference,  which  shows  that  the 
orchardists  are  almost  unanimous  in  holding  that  a  cold  spell  in  the 
spring  favors  the  development  of  curl. 

To  the  second  question,  as  to  whether  the  trees  were  most  affected  by 
curl  in  a  wet  or  drA^  season,  there  were  104  replies.  Of  these,  78 
stated  that  peach  trees  were  most  affected  in  wet  seasons,  8  that  they 
were  most  affected  in  dry  seasons,  and  18  that  there  was  no  diffei'ence. 
Here  again  is  seen  a  marked  agreement  in  the  replies,  a  great  majority 
of  the  growers  recognizing  that  wet  years  favor  the  disease. 
•  The  above-considered  conditions — a  cold  spell  in  the  spring  and  wet 
weather  —  may  be  explained  by  stating  that  such  conditions  favor,  on 
the  one  hand,  the  serious  development  of  the  fungus  causing  the  dis- 
ease, and,  on  the  other,  they  result  in  a  nuich  greater  susceptibility  of 
the  tissues  of  the  peach  leaves  to  the  attacks  of  the  parasite.  Where 
both  cold  and  rain  occur  together  in  the  spring,  about  the  tinu^  the 
leaves  are  pushing,  the  disease  is  liable  to  develop  seriously  and  few 
varieties  can  then  resist  it.  The  action  of  wet,  cold  weather  upon  the 
tissues  of  the  peach,  making  them  much  more  subject  to  curl  than  they 
otherwise  would  be,  has  been  considered  in  relation  to  other  plants  in 
a  paper  by  Prof.  H.  Marshall  Ward,*  who  says  that  vr/zt/^  thecomhined 
effect fi  of  tlie  physical  enviTOiiine)it  are  unfavorxible  to  the  host,  hut  not  so 
oi^  are  even  faiforalde  to  the  lyarasite,  we  find  the  disease  a.^.su//t  hi  r/  a  more 
(yr  less  jyvonounced  epidemic  character.  He  is  not  here  spetdcing  of  curl, 
but  the  statement  holds  perfectly  true  for  that  disease.  A  cold,  wet 
spell  succeeding  warm  spring  weather,  has  a  tendency  to  saturate  and 
soften  the  tissues  of  the  i)each,  as  in  the  case  of  other  plants.  The 
sudden  checking  of  active  transpiration,  due  to  lowered  temperature 
and  saturated  atmosphere,  soon  results  in  the  tissues  of  th(>  plant  being 
suffused  with  water.     ''The  stomata,"  as  Ward  puts  it,  "are  nearl}' 


^Wanl,   Prof.   II.  IVIarshall,  The  Relations  between  Host  and  Parasite  in  Certain 
Diseases  of  Plant^J,  Crooiiian  Ltctiiic,  I'mc  Ixoy.  Soc,  Vol.  XlyN'II,  No.  I'DO. 


24  PEACH    LEAF    CURL:    ITS    NATURE    AND   TREATMENT. 

closed,  the  cell  walls  hounding  the  intercellular  passages  and  the  air 
in  the  passages  themselves  are  thoroughly  saturated  with  water  and 
aqueous  vapor,  respectively,  and  the  movements  of  gases  must  be 
retarded  accordingly;  turgescence  is  promoted,  and  the  water  contents 
accunuilate  to  a  maximum,  owing  to  the  disturbance  of  equilibrium 
between  the  amounts  absorbed  by  the  active  roots  in  the  relatively 
warm  soil  and  those  passing  oft'  into  the  cold,  damp  air;  much  more 
water  is  absorbed  by  the  roots  in  the  relatively  warm  soil  than  passes 
ofl'  as  vapor  in  equal  periods  of  time."  Further  than  this.  Ward  states 
that  ""thc^  low  temperature,  feeble  light,  and  partially  ))locked  ven- 
tilation system  have  for  a  consequence  a  depression  of  respiratory 
activity  and  the.  absorption  of  oxygen  genei'ally."  This  must  give  a 
lowered  vitality  and  an  accumulation  of  organic  acids.  The  reduced 
light  also  leads  to  a  decided  reduction  in  the  assimilative  power  of  the 
leaves.  ''The  turgid  condition  of  the  cells,  and  the  diminished  inten 
sity  of  the  light,"  Ward  sa}\s,  ""will  favor  growth."  If  this  takes 
place,  "the  tendency  will  be  for  the  very  watery  cell  walls  to  become 
relatively  thinner  than  usual,  as  well  as  watery,  because  the  ill-nourished 
protophism  does  not  add  to  tlie  substance  of  the  walls  in  proportion. 
This  being  so,  we  have  the  case  of  thinner,  more  watery  cell  walls 
acting  as  the  onlv  mechanical  protection  between  a  possible  fungus  and 
the  cell  contents." 

It  is  generally  known  that  the  conditions  of  moisture  and  shade, 
which  are  above  shown  as  making  the  tissues  of  a  host  plant  more 
tender  and  watery  (more  svibject  to  fungous  attacks),  are  also  the 
conditions  most  favorable  to  the  development  of  fungi.  This  holds 
equally  as  good  for  Exoasciis  deformans  as  for  other  forms.  In  speak- 
ing of  these  conditions  in  relation  to  a  fungus  known  as  Botrytis^  Pro- 
fessor Ward  gives  some  generalizations  equall}"  applical)le  to  Exoascus 
def(yrmans  in  its  relation  to  curl.  He  says  that  just  those  external 
climatic  conditions  which  are  disturbing  the  well-being  of  the  green 
host  plant  are  either  favorable  to  the  fungi  considered  or,  at  awy  rate, 
not  in  the  least  inimical  to  their  development.  "Thus,"  he  sa3\s,  "the 
oxA^gen  respiration  of  the  fungus  goes  on  at  all  temperatures  from  0°  C. 
to  30'-'  C.  and  higher,  and  although  we  still  want  information  as  to 
details,  experiments  have  show^n  that  the  m3^celia  flourish  at  tempera- 
tures consideralily  below  the  optimum  for  higher  plants.  Moreover, 
light,  so  indispensable  for  the  carbon  assimilation  of  the  green  host, 
is  absolutel}'  unnecessary  for  the  development  of  the  fungus.  Then, 
again,  the  dull,  damp  weather  and  saturated  atmosphere,  so  injurious 
to  higher  vegetation,  if  prolonged,  because  they  entail  interference 
with  the  normal  performance  of  various  correlated  functions,  as  we 
have  seen,  and  render  the  plant  tender  in  all  respects,  are  distinctly 
favorable  to  the  development  of  these  fungi;  consequently  the  very 
set  of  external  circumstances  which  make  the  host  plant  least  able  to 


PHYSICAL    CONDITIONS    INKLUP^NOINO    THE    DISEASE.  25 

withstand  the  cntiT  aiul  (li'vasUition  of  a  parasitic  fungu.s  liki;  Jioliu/fls^ 
at  tlio  same  tiiiio  favor  the  dovolopiiiont  of  the  fiino-us  itself." 

The  writer  thinks,  as  the  result  of  ol)servatioiis  in  the  field,  that 
JExoasciu'i  di^forz/nnhs  is  favored  in  both  its  entrance  and  spread  within 
its  host  by  the  conditions  which  have  just  been  considered.  It  is  a 
widelv  observed  fact  that  leaf  curl  usualh^  develops  sparingly  in  a 
uniformly  warm  and  dry  spring,  and  it  is  also  noticed  that  where 
infection  has  occurred  a  return  of  wariii,  dry  weather,  or  even  the 
occurrence  of  a  hot,  dry  wind,  will  check  the  development  of  the 
fungus  within  the  tissues.  An  infected  leaf  may  fail  to  develop 
the  spores  of  the  fungus  under  such  circumstances.  The  thin,  satu- 
rated cell  walls  and  the  moist  intercellular  spaces  thus  appear  to  be 
closely  correlated  with  the  active  vegetation  of  the  fungus.  The 
growth  and  consequent  tenderness  of  the  tissues  is  also  important  in 
this  connection.  Where  soil,  elevation  of  orchard,  and  atmospheric 
conditions  are  unfavorable  to  a  Saturated  condition  of  the  plant  paren- 
chyma, the  disease  is  not  likel}'  to  run  more  than  a  short  and  feeble 
course.  Soil  and  elevation  are  here  considered  with  atmospheric  con-" 
ditions,  for  it  is  found  that  on  the  same  farm  a  difl'erence  of  elevation 
or  soil  moisture  may  determine  the  degree  of  virulence  of  the  disease. 
The  influence  of  elevation  may  be  of  onh"  secondary  nature — that  of 
maintaining  a  higher  temperature — but  its  action  on  the  disease  is  fre- 
quently well  marked.  Of  92  orchardists  who  expressed  their  views 
as  to  whether  trees  are  affected  b}^  curl  most  on  high  or  on  low  land, 
48  sa}^  that  trees  suffer  most  on  low  land,  14  on  high  land,  and  30 
think  there  is  no  difference.  While  the  majority  claiming  that  trees 
on  lovv'  land  are  most  affected  is  not  as  large  as  some  of  the  majorities 
obtained  in  replies  to  other  questions,  it  represents  over  one-half 
the  replies  received  to  the  question  under  consideration  and  is  more 
than  three  times  as  great  as  the  number  who  lielieve  trees  to  be  most 
affected  on  high  land,  hence  is  sufficient  to  estal)lish  confidence  in  its 
reliabilit}',  even  if  it  were  not  indorsed  bv  many  published  statements 
to  the  same  effect. 

Mr.  Thomas  A.  Sharpe,  superintendent  of  the  experiment  farm  at 
Agassiz,  British  Columbia,  has  made  several  comparative  reports  on 
the  action  of  peach  leaf  curl  on  trees  planted  in  the  valley  and  upon 
the  more  elevated  bench  lands  of  the  farm.  A  few  brief  statements 
from  these  reports  should  be  of  value  in  connection  with  the  above 
statements.^  In  1892,  Mr.  Sharpe  says,  the  peach  trees  suffered  from 
a  severe  attack  of  leaf  curl.  ''Only  5  varieties  of  those  planted  in 
the  valley  escaped"  the  disease.  ''The  trees  planted  on  the  bench 
lands  did  not  suffer  so  much,  and  appeared  to  recover  much  more 
rapidly  than  those  in  the  valley"  (1.  c,  p.  278).     In  1893,  it  is  said, 

'  See  report;^  f)f  experimental  farms,  Ottawa,  Canada,  for  the  years  indicated. 


26     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

the  curl  leaf  in  the  pencil  unci  iiecturine  trees  was  worse  than  it  had 
ever  been  before,  the  Malta  l)eing  the  only  variety  that  was  entirely 
healthy  on  level  land.  The  varieties  received  from  Eng-laiid  and 
planted  on  the  level  land  were  just  as  badl}^  affected  as  the  otliers. 
The  first  and  second  bench  orchards  suffered  alike  with  those  on  the 
level  j:;r()und,  but  the  orchard  hig-hest  up,  at  an  elevation  of  800  feet, 
had  no  curl  in  any  case,  and  the  trees  appeared  to  have  suffered  less 
from  cold  than  those  lower  down  (1.  c,  p.  342).  Mr.  Sharpe  says 
that  in  1896,  "as  heretofore,  the  trees  on  the  upper  benches,  both 
nectarine  and  peach,  escaped  the  curl  leaf  entirelv"  (1.  c.,  p.  -MO). 
Again,  it  is  said  that  "the  peach  crop  on  the  level  land  this  year  [in 
1898]  was  almost  an  entire  failure.  The  curl  leaf  was  ver}"  prevalent, 
nearly  every  tree  being  seriously  affected  by  it.'"  Relating  to  the 
orchard  on  the  bench  lands,  it  is  stated  that  "curl  leaf  did  not  affect 
the  foliage  there;  in  fact,  it  has  never  injured  the  foliage  on  either 
peach  or  nectarine  trees  on  the  })enches  over  300  feet  above  the 
valley"  (1.  c,  p.  -lOS).  These  facts  have  an  especial  interest  and 
value  in  that  they  were  recorded  by  a  single  observer  on  one  farm 
and  during  successive  years  and  epidemics  of  curl,  and  thej^  are  in 
perfect  harmony  with  the  experience  of  a  majority  of  the  growers 
whose  views  are  presented  above. 

The  soil  ma}^  exert  its  influence  by  abundantly  or  feebly  supplying 
the  transpiration  stream,  in  accordance  with  the  degree  of  accessibility 
of  the  moisture  it  contains,  to  the  root  hairs  of  the  tree.  It  may  he 
said,  however,  that  as  leaf  curl  commonly  develops  at  the  beginning 
of  spring  growth  or  at  the  close  of  the  winter's  rains,  the  soil  will 
rarely  be  found  so  deficient  in  moisture  as  to  greatly  retard  the  devel- 
opment of  the  disease  where  other  conditions  are  fa^'orable.  It  is  prob- 
ably equally  true  that  the  excess  of  water  usually  found  in  the  soil 
in  the  spring  is  favorable  to  the  special  development  of  the  disease  at 
that  season  in  its  worst  form. 

Besides  the  influence  of  temporary  excessive  humidity  of  the  atmos- 
phere upon  leaf  curl,  which  has  already  l)een  considered,  there  are 
other  atmospheric  influences  and  relations  of  importance,  which  depend 
upon  the  local  or  general  geographic,  topographic,  and  climatic  fea- 
tui'es  of  country.  Some  of  theso  more  prominent  atmospheric 
influences  nui}'  here  be  briefly  considered,  together  with  their  most 
probable  causes. 

Proximity  to  large  l)odies  of  water,  whether  salt  or  fresh,  greatly 
favors  the  development  of  curl.  The  cause  for  this  clearly  rests  in  the 
resulting  greater  humidity  and  lower  temperature  of  the  atmosphere. 
Plants  growing  in  a  constantly  humid  atmosphere  have  normally  more 
succulent  and  tiMider  tissues  than  those  growing  in  a  drier  region.  The 
reasons  for  this  have  already  been  alluded  to  for  special  cases  of 
extreme  atmospheric  humidity  and  lowered  temperature.     Near  large 


PHYSICAL    CONDITI<>NS    TNKLUENCINO    TITK    DISEASE.  27 

l)()(li('s  ot^  water  si)riiio-  t"()<^s  coinmonly  occur,  and  those  lead  to  the 
increase  of  the  atmospheric  huinidity  at  a  time  whiMi  th(^  t'oliat>-e  is 
tender  and  orowiny- rapidly,  thus  stimulating-  a  development  of  curl 
almost  amuiall}'  and  over  wide  stretciu's  of  country.  lnde[)en(lent  of 
fogs,  the  atmosphere  about  large  bodies  of  water  is  also  nuicli  more 
huiuid  than  in  an  inland  i-egion.  Instances  of  th(>  influence  of  large 
l)odies  of  water  on  the  general  prevalence  and  fre(pient  occurrence^  of 
curl  in  a  region  are  found  in  western  New  York,  near  the  shoi-e  of  Lak(^ 
Ontario;  in  Ontario.  Canada,  near  Lakes  Erie  and  Ontario;  in  Michi- 
gan along  the  shore  of  Lake  jNlichigan;  in  Oaliforida  about  the  )»ay  of 
San  Francisco  and  at  other  points  along  the  Pacilic  coast:  in  ^Vashing- 
ton  and  British  Columl)ia  a])out  Puget  Sound;  and  in  many  similar 
situations  in  all  portions  of  the  world  where  the  pcnich  is  grow' n.  The 
writer  believes,  however,  that  the  influence  of  large  ])odies  of  water 
upon  the  development  of  curl  depends  in  part  upon  the  normal  spring 
temperature  of  the  region,  and  likewise  upon  the  source  of  the  prevail- 
ing winds.  Where  the  prevailing  spring  winds  are  from  a  dry,  inland 
region  instead  of  from  the  water,  the  atmosphere  does  not  feel  the 
influences  of  the  latter.  Moreover,  where  the  spring  temperature  is 
high,  transpiration  may  proceed  normal!}^  even  in  the  neighborhood  of 
large  bodies  of  water,  and  curl  may  not  commonly  prevail. 

In  contrast  to  the  influences  of  large  ])odies  of  water  are  those  of 
neighboring  dry  and  atid  plains  or  desert  regions.  In  the  midst  of 
such  influences  peach  leaf  curl  can  rarely  attain  to  an  epiphytotic 
development,  and  then  only  under  special  favoring  seasonal  condi- 
tions. The  atmosphere  is  normally  too  dry  in  such  situations  to  exert 
a  predisposing  action  upon  the  host,  and  it  certainly  does  not  favor 
the  serious  development  of  the  parasite.  Exemplifying  these  condi- 
tions are  large  areas  in  Arizona,  New  Mexico,  Nevada,  Utah,  Colorado, 
Texas,  Kansas,  and  California.  Little  or  no  curl  is  reported  from  the 
more  arid  portions  of  these  sections  of  the  country,  its  absence  being 
due,  at  least  in  part,  to  the  influences  here  considered. 

Another  of  the  broader  influences  afi'ecting  the  general  and  perma- 
nent prevalence  of  curl  over  extensive  regions  is  the  normal  amuial 
rainfall.  Comparisons  of  this  kind  must  be  made,  howe\'er,  between 
regions  of  approximately  similar  temperatur(\  Under  such  condi- 
tions it  may  be  said  that  the  general  amuial  prevalence  of  leaf  curl 
increases  with  the  increase  of  normal  annual  precipitation.  Compari- 
sons of  this  kind  can  hardly  be  justly  drawn  in  the  ^Mississippi  Valley 
or  on  the  Atlantic  coast,  as  the  temperature  conditions  vary  too 
greatly  in  those  regions  from  north  to  south.  On  the  Pacitic  coast, 
however,  owing  to  the  modifying  influence  of  the  Pacific  Ocean,  the 
temperature  prevailing  from  Lower  California  to  British  Cohunbia, 
a  distance  of  about  one  thousand  three  hundred  miles,  presents  no 
such  o-reat  variations  as  are  found  in  a  like  distance  from  south  to 


28     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

north  on  the  Atlantic  coast,  ,so  that  the  relations  of  annual  rainfall  to 
the  constant  prevalence  of  curl  ma}^  be  more  fairly  decided. 

In  the  following  remarks  on  this  subject  I  have  left  out  of  consid- 
eration the  temporary  influence  of  exceptional  seasons  and,  as  far  as 
possible,  the  special  influence  of  local  features.  The  subject  should 
be  viewed  from  the  liroad  field  above  pointed  out.  In  southern  Cali- 
fornia leaf  curl  is  not  recognized  as  a  generally  prevalent  and  serious 
trouble,  but  there  is  evidence  which  shows  that  its  prevalence  increases 
from  San  Diego  northward  to  the  San  Bernardino  Mountains.  The 
average  annual  rainfall  varies  from  about  10  inches  at  the  former  place 
to  10  inches  at  Los  Angeles,  which  is  not  far  from  the  mountains.  In 
the  San  Joaquin  Valley  the  prevalence  of  curl  increases  as  a  whole  from 
the  south  central  portion  toward  Sacramento  and  the  north.  The 
average  annual  rainfall,  which  is  7  inches  at  Tulare,  9  inches  at  Fresno, 
11  inches  at  Merced,  and  14  inches  at  Stockton,  reaches  20  inches  at 
Sacramento,  about  which  center  curl  is  quite  prevalent.  The  average 
rainfall  at  Oaldand  is  23  inches,  and  curl  is  quite  troublesome  there. 
In  the  Sacramento  Valley  curl  is  frequently  quite  prevalent,  and  the 
rainfall  \aries  from  20  inches  at  Sacramento  and  Chico  to  34  inches  at 
Kedding.  About  Ashland,  in  southern  Oregon,  the  rainfall  is  23 
inches,  and  the  disease  is  about  as  in  the  Sacramento  Valley.  Farther 
north  in  Oregon  curl  becomes  decidedly  more  prevalent  and  injurious 
at  the  west  of  the  Cascade  Mountains,  and  increases  as  Portland  is 
approached.  The  rainfall  is  35  inches  at  Roseburg,  4()  inches  at 
Albany,  and  49  inches  at  Portland.  From  Albany  to  Portland  the 
peach  industry'  has  been  greatly  injured  bj-  curl,  and  on  its  account 
many  growers  in  this  region  have  considered  peach  culture  a  failure. 

Curl,  it  seems,  was  introduced  into  the  central  ])art  of  the  Willamette 
Valley,  Marion  County,  nearly  half  a  century  ago.  Prior  to  that 
time  the  peach  was  successfully  grown  in  that  region  in  spite  of  the 
humidity  of  the  climate.  In  the  Patent  Office  Report  for  1855,  p. 
298,  there  is  a  statement  of  the  situation  in  Polk  and  Marion  counties 
from  1852  to  1855.  This  statement  was  from  Mr.  Amos  Harry,  of 
Farm  Valley,  Polk  County,  Oreg.,  and  is  of  special  interest  in  this 
connection.  Mr.  Harrj- says:  "The  peach  in  this  county  has  been 
afiected  with  a  disease  known  as  the  'curled  leaf.'  which  threatens  to 
destroy  the  trees.  It  made  its  appearance  at  Mill  Creek,  in  Marion 
County,  in  1852,  and  extended  considerably  on  that  side  of  the  river 
(Willamette  River)  in  1853,  but  had  reached  most  parts  of  the  valley 
in  1854-55.  Some  trees  seem  to  escape  it  nuich  more  than  others,  but 
if  the  malady  increases  for  two  years  to  come  as  it  has  for  two  past,  I 
fear  we  shall  come  entirely  short  of  this  delicious  fruit.  Some  think 
it  is  owing  to  cold,  wet  weather,  and  recommend  shortening  all  the 
limbs  as  a  remedy,  and  some  experiments  seem  to  favor  this  idea. 
Others  think  it  is  produced  by  an  insect,  and  that  no  remedy  will  save 
the  trees  unless  it  can  be  applied  to  the  ivhole  surface  of  the  leaves." 


PHYSICAL   (M»NDIT1(>NS    I  ni<'lup:ncin(^   thk    diskask.  2U 

'V\w  r;iiii1":ill  at  rortliiiid,  as  already  said,  is-ll>  iiiclu's,  atid  curl  iscoin- 
moiily  prevalt'iit  and  sovcnv.  At  llinatilla,  cast  of  the  Cascade  Moun- 
tains. l)ut  al»()ut  the  same  distance  north  as  Portland,  the  rainfall  is 
only  1<>  inches,  while  on  that  side  of  tlic  mountains  the  peach  industry 
i>;  extiMisive  and  everywhere  prospiM'ous,  leaf  curl  liein*"'  much  less 
prevalent  and  of  secondary  importance.  This  shows  that  it  is  not  the 
distance  north  and  the  consecjuent  lower  temperature  which  makes  curl 
more  severe  at  Portland  than  at  Los  Angeles  for  insttince,  l)ut  that  it  is 
the  excess  of  rainfall,  for  at  the  east  of  the  mountains,  near  Umatilla, 
the  temperature  goes  equally  as  low  or  lower  than  at  Portland,  and 
curl  is  of  little  importance  there.  In  the  Pu^-et  Sound  i-eoion  peach 
culture  has  never  developed  extensively,  the  general  prevalence  of  curl 
and  its  injurious  action  being  one  of  the  chief  reasons.  The  rainfall 
is  50  inches  at  Seattle  and  5(5  inches  at  Olympia.  It  is  only  T  inches 
at  Kennewick  and  !>  inches  at  Ellensburg,  on  the  east  side  of  the  Cas- 
cade Range.  The  peach  orchards  of  North  Yakima  and  .neighboring 
sections  on  the  east  side  of  the  Cascades  and  near  Ellens) )urg,  where 
this  rainfall  is  taken,  are  noted  for  their  extent,  thrift,  and  general 
health,  and  curl  is  not  a  serious  trouble.  This  case  is  parallel  with 
that  of  Portland,  already  considered.  The  rainfall  at  the  west  of  the 
mountains  is  50  to  50  inches  or  more,  while  at  the  east  it  is  only  7  to 
9  inches.  In  the  former  region  peach  growing  is  not  listed  ])y  the 
Washington  Board  of  Horticulture  as  one  of  the  horticultural  indus- 
tries, but  in  the  latter  region  the  peach  is  a  leading  fruit,  lieing 
extensively  and  successfully  grown.  The  winter  temperature  east  of 
the  mountains  should  range  fully  as  low  where  the  peaches  are  grown 
as  at  the  west  of  the  range.  The  contrast  in  peach  culture  in  the  two 
situations  results  from  the  difference  of  rainfall,  and  the  heavy  rain- 
fall at  the  west  of  the  Cascades  results  in  a  developnuMit  of  curl  almost 
prohibitive  to  peach  growing.' 

In  replying  to  a  circular  letter  sent  to  the  peach  growers  of  Mary- 
land, November,  1893,  Mr.  T.  C.  Stayton,  of  Queen  Amie,  makes  some 
statements  which  bear  directh'  on  the  matter  here  considered  and  are 
of  nmch  interest  as  resulting  from  personal  observation.  After  speak- 
ing of  the  conditions  in  Maryland,  Mr. '  Stayton  savs:  "I  was  in 
Washington  State  during  the  months  of  April,  May,  June,  etc.,  this 
year,  and  I  find  they  can  not  grow  peach  trees  west  of  the  Cascade 
Mountains  or  in  western  Washington,  as  that  part  of  the  State  is 
called,  as  that  is  a  A'ery  wet  part  of  our  country."  He  adds  that  this 
was  especially  true  in  1893,  and  continues:  '"About  all  the  young  trees 
that  had  been  planted  in  that  pai-t  of  the  State  died  fi'om  curl  leaf,  or 
so  nearly  so  that  they  were  worthless,  ])ut  over  in  eastern  ^^'ashiIlgton 
I  did  not  notice  any  curl  leaf,  the  climate  being  dry." 

^  For  a  full  and  accurate  account  of  the  rainfall  conditions  prevailing  on  the 
Pacific  coast,  see  Report  of  the  Rainfall  on  ttie  Pacific  Slope  for  from  Two  to  Forty 
Years,  AVashington,  1889;  also  other  reports  of  the  Weather  Bureau. 


30         I'KAOH  lp:af  curl:  its  nature  and  treatment. 

Peach  l(>af  curl  appears  to  ])e  more  prevalent  in  late  tlian  in  earh'' 
springs.  This  is  pro))al)ly  due  to  the  lower  temperature  and  greater 
rainfall  usually  accompanying  the  former.  Of  80  growers  who  gave 
their  experience  in  relation  to  this  matter,  43  stated  that  curl  affects 
trees  most  in  late  springs,  23  believed  it  affects  them  most  in  early 
springs,  and  l-i  had  noticed  no  difference. 

The  question  as  to  whether  peach  leaf  curl  affects  trees  most  after  a 
cold  or  warm  winter  was  submitted  to  the  growers,  and  of  the  67  who 
replied,  27  stated  that  trees  were  most  affected  after  a  cold  winter,  21 
that  they  were  most  affected  after  a  warm  winter,  and  id  growers  had 
observtnl  no  difference. 

The  ([uestion  of  the  influence  of  heav}'  dews  on  curl  was  also  sub- 
mitted to  the  orchardists,  and  the  views  expressed  in  their  replies 
exlii])it  a  remarkable  agreement,  47  out  of  the  58  expressions  of 
opinion  received  stating  that  the  disease  is  no  worse  after  a  series  of 
heavy  dews.  To  the  writer  it  appears  probable  that  these  answers  are 
in  perfect  accord  with  the  facts.  Heavy  dews  can  exert  l)ut  slight 
influence  upon  the  tissues  of  the  peach,  as  they  occur  at  night,  when 
,  transpiration  from  the  leaf  is  largely  checked  by  the  reduced  light  and 
lowered  temperature  of  the  atmosphere,  resulting  in  the  stomata  being 
nearly  closed.  With  the  return  of  light  and  warmth  the  dew  evapo- 
rates with  the  resumption  of  transpiration,  and  can  have  but  little 
influence  upon  the  tissues  of  the  leaf.  It  might  seem  that  dew  would 
have  a  direct  action  on  the  germination  of  the  spores  of  the  fungus 
and  in  that  way  lead  to  a  serious  development  of  the  disease  after  one 
or  more  heavy  dews.  This  view,  however,  is  not  supported  by  observa- 
tions either  in  the  field  or  in  the  laboratory.  In  regions  having  little 
cloudy  weather,  with  exceptionally  clear  sky,  as  in  many  portions  of 
the  Southwest,  the  heat  of  the  soil  radiates  rapidly  after  sunset.  In 
such  sections  of  the  country  the  days  are  hot  and  the  nights  cool  or 
cold  in  comparison,  the  range  of  temperature  between  night  and  day 
being  often  considerable.  In  such  regions  dew  is  conmion  and  often 
heavy,  but  it  is  here  that  least  curl  occurs. 

Relative  to  the  action  of  dew  on  the  germination  of  the  spores  of 
ExoasiCKs  dcformam^  it  may  be  said  that  something  more  than  dew  is 
required  for  such  germination.  The  writer  has  tested  this  matter 
most  thoroughly,  not  only  with  dew,  but  with  many  forms  of  culture 
media  at  various  temperatures  and  with  varying  supplies  of  oxygen. 
Bi-cfeld  has  also  shown  that  moisture  alone  is  not  sufficient  for  germi- 
nation, behaving  utterly  failed  to  induce  germination  in  a  single  instance 
after  months  of  work  with  culture  media  in  liquid  form.  Budding  of 
the  spores  is  eas}^  to  obtain  in  all  liquids,  and  is  more  abundant  and 
continuous  in  sidtable  nourishing  cultures  than  in  dew  or  rain  water. 
Fiftv-eight  growers  replied  to  an  inquiry  on  this  subject,  47  stating 
that  the  disease  is  no  worse  after  a  series  of  heav}^  dews,  7  that  it 
is  worse,  and  4  that  no  difference  was  observed. 


THE     DIRECT    CAUSE    (»K    I'EACJI     LEAK    (MIRL.  31 

THE    EINIRIS    CAi;siN(!    THE    DISEASE. 

The  fungus  i-:uisiiiu-  peach  leaf  curl,  now  known  as  Krixisciisdrforimiiis 
(Bork.)  Fuckol,  is  a  incuihor  of  the  subfamily  of  fuii««i  known  as 
Ki't)((f<ce(t>.  The  /i'/v>^^s•aY^  arc  low  or  simple  Aacomycetc.s^in'  funt>-i  hear- 
ino-  their  spores  in  cases  or  usci. 

The  classification  of  the  Enxm-i'iv  which  now  lavs  o"reatest  claim  to 
seientihc  permanence  is  that  outlined  in  the  recent  writings  of  Sade- 
beck,  who  has  given  careful  study  to  these  forms.  ^ 

Of  the  five  genera  which  he  recognizes,  only  the  last  directlv  concerns 
us  at  this  time,  as  it  is  to  this  genus  {Exodseui^)  that  the  peach  curl 
fungus  belongs,  as  well  as  numerous  other  species  injurious  to  horti- 
culture. In  considering  this  genus  Sadebeck  ~  has  grouped  thirty  of 
its  species  according  to  certain  characters  of  development.  He  recog- 
nizes the  following  characters  of  the  genus : 

ExoAscrs  Fuckel. 

A.  The  myceliimi  is  perennial  in  the  inner  tissues  of  the  axial  organs. 

a.  The  development  of  the  hymenium  occurs  only  in  the  floral  leaves  of  the 
host  plant.     Eight  species. 

h.  The  development  of  the  hymenium  occurs  only  in  tlic  foliage  leaves  of  the 
host  plant.     Seven  species,  including  E.  deformaiif:.^ 

(-.  The  development  of  the  hymenium  occurs  upon  the  leaves  as  well  as  uiion  the 
fruits.     One  species. 

B.  The  mycelium  is  perennial  in  the  buds  of  the  host  plant  and  de\-elops  only 
subcuticularly  in  the  leaves. 

^Sadebeck,  Dr.  R.,  Die  parasitischen  Exoasceen,  Hamburg,  1.S93,  ]>.  43. 
Sadebeck  recognizes  five  genera  in  the  Exoasce<r,  which  he  aj-ranges  and  character- 
izes in  the  following  manner: 

EXOASCE.E:  Ascomycetes  whose  asci  are  not  united  in  a  fruit  body. 

A.  The  asci  arise  as  swellings  at  the  end    of   the  branches  of  the  mycelial 
threads. 

1.  Endomijcrs  Tulasne.  Four-spored  asci,  no  conidia  within  the  same;  the  sterile 
threads  develoi?  chlamydospores  and  oidia. 

2.  MiigmmrUd  Sadebeck.  Parasitic.  Asci  with  more  than  four  spores;  usually 
conidia  formations  in  the  ascus.     Oidia  and  chlamydospores  wanting. 

B.  The  asci  take  their  origin  from  a  more  or  less  loose  hymenium. 

3.  Ascocortichnn  Bref.  Saprophytic  on  bark.  '  The  ascus  layers  are  arraiiged  in  a 
loose  hymenium  upon  the  mycelium. 

4.  Taphrina  Fries.  Parasitic.  Without  perennial  mycelium.  In  the  formation 
of  the  ascogenous  cells  differentiations  of  material  occur.     Forming  leaf  si)ots. 

5.  E.wascus  Fuckel.  Parasitic.  With  i)erennial  mycelium.  In  the  formation  of 
the  asci  no  differentiations  of  material  appear.  The  sul)cnticular  mycelium  changes 
directly  to  ascogenous  cells.     Causing  sprout  deformations. 

■^Sadel)eck,  Dr.  R.,  Einige  neue  P>eol)achtungen  und  kritische  Bemerkungen  iiber 
die  Exoascacese,  pp.  277, 27S,  reprint  from  den  Ber.  d.  deutsch.  ])ot.  Ges.,  1895, 
Bd.  XIII. 

*Dr.  von  Derschau  has  described  the  occasional  fruiting  of  E.ioftsciis  deformans  in 
the  blossoms  of  the  peach.  The  ligures  given  by  this  author  do  not  show  the  nor- 
mal development  of  ascogenous  cells  \n  the  l)lossoms  which  are  so  common  in  the 
leaf  blade  of  the  peach.  His  figures  show  the  asci  as  arising  from  lateral  branches 
of  a  continuous  mycelial  liyi)ha,  and  this  mycelium  is  situated  beneath  the  epidermal 
cells  instead  of  between  the  cuticle  and  ei)idermis  (Landw.  Jahrb.,  Berlin,  1897,  pp. 
897-901,  and  Table  XLI) . 


32     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

ii.  The  development  of  the  liyiiu'iiinni  occurs  only  in  tlie  floral  U-aves  of  tluOiost 
plant.     Three  species. 

h.  The  development  of  the  hyineninni  occurs  only  upon  the  foliage  leaves.  Ten 
species. 

V.  The  resting  mycelium  extends  intercellularly  in  the  deformations  of  the  leaves. 
One  species. 

It  may  be  seen  under  A  h  of  thi.s  arrangenient  that  Exomcvs  defor- 
mans is  said  to  possess  perennial  mycelium,  inhabiting  the  inner  tis- 
sues of  the  axial  organs,  and  that  the  development  of  the  hymenium 
oeeurs  only  in  the  foliage  leaves  of  the  host  plant.  As  will  be  seen  in 
another  part  of  this  ))ulletin,  it  is  perhaps  a  perennial  nature  of  the 
mycelium  of  E.  dfforvums  which  makes  it  difficult  to  thoroughly  rid 
an  orchard  of  curl  l)y  means  of  spray  treatment,  but  this  matter 
requires  further  careful  consideration. 

The  sjnionymy  of  Exoancm  defonnans  (Berk.)  Fuckel  has  been 
given  by  numerous  writers.     Sadebeck^  gives  it  as  follows: 

Ascoim/ces  deformanfi  Berk.     Intro,  to  Cryptogamic  Botany,  1857,  p.  284. 

Ascoaporhun  deformans  Berk.     Outlines,  1860,  p.  449. 

Taphriim  deformnni^  Tul.     Ann.  Sci.  Nat.,  1866,  V.  S^r.,  t.  5.,  p.  128. 

Exonttrna  defoniicnis  Fuckel.      (o)   Perm-tc  Fuck.     8yml)ol;«  Micolog.,  1869,  p.  252. 

This  fungus  has  been  very  commonl}-  observed  and  frequently 
described  by  ))otaiiists  since  Berkeley  called  attention  to  it  in  1857. 
It  has  thus  l)een  known  as  the  cause  of  curl  for  a  little  less  than  half 
a  century.  The  peculiar  l)ehavior  of  peach  foliage  under  its  action 
has  been  observed  l)v  horticulturists,  however,  for  a  much  longer 
time.  The  disease  was  well  descrilied  in  England  in  the  early  part  of 
the  present  century. 

In  spite  of  tlie  A'cry  common  appearance  of  Exoasats  deformans 
upon  peach  foliage  in  peach-growing  countries,  the  descriptive  litera- 
ture relating  to  its  life  history  is  not  free  from  conflicting  statements. 
Several  species  of  Exoascew  have  been  confounded  with  this  species 
in*  some  instances,  and  subsequent  writers  have  perpetuat(xl  the 
confusion. 

Some  earlier  writers  l)elieved  this  species  inhabits  a  considerable 
number  of  host  plants,  thus  resulting  in  the  description  and  distribu- 
tion of  several  distinct  species  as  Exoascus  deformans.  To  avoid  such 
confusion  it  would  be  best  to  confine  remarks  upon  this  species  to  the 
fungus  as  it  develops  upon  the  peach  {Prunus  persica  L.),  which  if 
not  its  onl}^  host,  is  certainly  its  most  com-mon  one. 

At  least  two  modes  of  infection  of  the  peach  tree  by  Exoascus 
deformans  are  said  to  exist — (1)  by  means  of  perennial  mj^celium, 
and  (2)  by  means  of  the  spores  of  the  f  luigus. 

Sadebeck^  is  authority  for  the  statement  that  the  mycelium  winters 
over  in  the  5''oungest  portions  of  the  one-year-old  branches  of  the  host 

'  Radebeck,  Dr.  E,.,  Die  parasitischen  Exoasceen,  Ham1)urg,  1893,  y>.  53. 
•■'Idem.  1.  c. 


THE    INFECTION    OF    THE    HOST.  33 

])hmt.  unci  iiuiy  hv  seen  in  the  priniary  oortox.  in  the  lut'diilla.  and  in 
the  niedullary  I'ays  of  the  first  shoots  of  each  period  of  veo-ctation, 
but  has  not  l)oen  observed  in  the  soft  bast.  With  the  be^innin^-  of 
the  new  season  of  growth  the  luyeeliuni,  aceording  to  Sadebeck, 
extends  into  the  leaves  of  the  young  shoots,  penetrates  first  the  inner 
tissue  of  the  halves,  and  finally  i)r()gresses  to  the  deveh)pinent  of  the 
subeutieular  hymeniuni.  From  what  foundation  of  experimentation 
Sadebeck  has  arrived  at  these  views  respecting  this  particular  species, 
I  :un  unabl(>  to  state,  but  lie  has  giviMi  th(>  outlines  of  his  investigations 
upon  other  species.' 

The  facts  given  by  De  liarv  '  can  not  be  cited-  here,  for  this  work 
was  done  upon  the  Exoascus  infesting  the  cherry  tree,  and  which  is 
now  considered  to  be  distinct  from  J^J.  deformans. 

The  general  acceptance  of  the  view  that  spring  infection  of  the  peach 
foliage  is  largely  due  to  the  extension  of  the  internal  perennial  myce- 
lium into  the  new  shoots  and  leaves  from  the  shoots  of  the  previous 
sunnner,  has  probably  considerably  retarded  the  progress  of  prevent- 
ive treatment.  Pathologists  have  thought  it  improbable  that  an}^ 
considerable  amount  of  disease  could  be  prevented  after  a  tree  was 
once  generally  affected,  as  the  perennial  mycelium,  being  internal, 
could  not  be  readily  reached  by  external  sprays.  Prillieux,''  writing 
in  1872,  advises  the  gathering  of  the  diseased  leaves  and  the  cutting 
away  and  burning  of  the  diseased  branches.  Frank  *  has  made  like 
reconnnendations  in  both  editions  of  his  work  on  plant  diseases. 
Assuming  the  mycelium  to  be  perennial,  he  says  that  the  curing  of  the 
disease  might  be  aimed  at  through  cutting  back  of  the  diseased  branches 
and  the  prevention  through  quick  removal  of  the  diseased  leaves. 
Winter'  suggests  a  somewhat  similar  line  of  treatment,  with  the 
additional  recommendation  that  the  trees  be  protected  from  rain 
during  the  unfolding  of  the  leaves.  Dr.  Cobb/'  as  late  as  1892,  after 
speaking  of  the  perennial  mycelium  of  this  fungus,  discusses  pre- 
ventive and  curative  measures,  such  as  the  destruction  of  diseased 
leaves,  prunings,  etc.,  while  in  the  more  severe  cases  he  says  the 
sooner  the  trees  are  cut  down  and  Inirned  the  better  it  will  be  for  the 
peach  industry. 

^  Sadebeck,  Dr.  R.,  Die  parasitischen  Exoasceen,  Hamburg,  1893,  pp.  24-28. — Das 
perennirende  Mycel  der  Exoapcus-Arten. 

'■'De  Bary,  A.,  Com.  Mor.  and  Biol,  of  the  Fun<ri,  Mycetozoa,  and  Bat-teria,  Eng- 
\\^\\  edition,  1887,  p.  266. 

M'rillieux,  Ed.,  Bui.  de  la  hoc.  hot.  de  Franre,  1872,  T.  XIX,  \k  -!<>• 

*  Frank,  Dr.  A.  B.,  Die  Krankheiten  der  Pflanzen,  lireslau,  1881,  Part  11,  p.  526; 
second  edition,  1896,  Vol.  II,  p.  250. 

^Winter,  Dr.  Georg,  Die  durch  Pilze  verursachten  Kranklicilcu  der  Kultiirj,'e- 
wiichse,  Leipzig,  1878,  p.  47. 

"Cobb,  Dr.  N.  A.,  The  Agricultural  (iazette,  Sydney,  New  South  Wales,  IS92,  Vol, 
III,  pp.  1001-1004. 

19093— No.  20 3 


34     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

Relative  to  the  use  of  fungicides  the  same  writer  says:  "These 
treatments  are  of  doubtful  value  as  far  as  the  curl  is  concerned,  and 
were  it  not  that  they  arc  useful  in  other  waj'S  I  would  not  mention 
them."  It  is  evident  that  these  views  are  the  result  of  Dr.  Cobb's 
belief  that  the  perennial  mycelium  is  responsible  for  the  major  portion 
of  the  spring  infection  of  the  tree.  The  writings  of  others  to  the 
same  effect  could  be  cited,  but  the  views  of  the  workers  already  named 
are  sufficient  to  show  that  their  recommendations  for  treatment  have 
been  based  upon  the  hypothesis  that  the  spring  infection  could  not  be 
prevented  by  treatment  with  fungicides,  as  it  arose  mainly  from  in- 
ternal mycelium  rather  than  from  the  germination  of  external  spores. 
That  this  view  has  held  l)ack  the  preventi^•e  treatment  of  the  disease, 
as  already  claimed,  can  not  be  doubted,  and  that  a  perennial  mycelium 
is  not  responsible  for  more  than  a  very  small  percentage  of  the  spring 
infections  seems  evident  from  the  results  of  the  present  experi- 
ments; in  fact  it  may  even  be  questioned  if  such  infection  takes  place 
except  under  exceptionally  favorable  conditions.  Our  experiments 
have  demonstrated  that  as  high  as  98  per  cent  of  infections  may  be 
prevented  by  a  single  thorough  application  of  a  suitable  fungicide. 
This  is  as  high  a  percentage  of  control  as  is  often  obtained  in  the 
treatment  of  fungous  diseases  where  no  perennial  mycelium  exists, 
and  it  seems  probable  that  the  infections  by  this  means  ma}'  not  com- 
monly exceed  5  per  cent  of  each  spring's  infections.  Were  this  not 
the  case  we  would  be  forced  to  assume  that  the  spray  has  a  direct 
effect  upon  the  hibernating  mycelium,  which  certainly  would  be 
unusual  and  scarceh'  to  be  expected. 

The  second  mode  of  spring  infection — that  by  means  of  spores — is 
probably  much  more  general  and  important  in  this  disease  than  has 
been  supposed.  That  90  to  98  per  cent  of  the  infections  of  the  tree 
are  prevented  l)y  a  single  spraying  suggests  that  at  least  such  percent- 
age of  the  infections  is  by  means  of  spores. 

The  m3a'elium  of  Ji'xonsci/s  dtfornxinx  as  found  in  the  peach,  shows 
great  differences  in  the  form  and  appearance  of  its  hyphiv.  These 
differences  depend  upon  the  stage  of  development  of  the  fungus  and 
the  various  functions  of  the  mycelium.  The  writer  recognizes  three 
types  of  hyphie,  which  may  be  termed  vegetative,  distributive,  and 
fruiting. 

The  vegetative  hypha?  are  found  most  commonly  in  the  leaf  paren- 
chyma, l)ut  are  also  met  with  in  the  leaf  stalk  and  cortical  parenchyma 
of  badly  diseased  and  distorted  liranches.  Thes(>  hypha>  may  be  most 
distinctly  seen,  and  are  most  highly  developed,  in  infested  leaves  which 
have  not  yet  formed  the  hymenium  of  ascogcnous  cells,  but  in  which 
the  parasite  has  been  present  a  sufficient  time  to  entirely  alter  the 
character  of  the  palisade  tissue  and  cause  the  loss  of  the  chlorophyll. 
In  the  leaf  blade  the  palisade  tissue  tirst  shows  the  serious  action  of 


BULL.  20,  DIV.  VEQ.  PHYS.  &  PATH,  U.  S.  DEPT.  AGRICULTURE. 


PLATE   II. 


MYCELIUM    OF    EXOASCUS    DEFORMANS,    THE    FUNGUS 


CAUSING    PEACH    LEAF    CURL. 


A.H<,eii«.  (•o.l.iih.Bailiitu.r. 


DESCRIPTION  OF   PLATE  11. 

Mycelium  of  Exoascus  deformans  (600/1) .  Figs.  1  and  2,  normal  vegetative  hyphfe, 
as  found  in  the  leaf  parenchyma,  showing  characteristic  septation,  modes  of  branch- 
ing, etc. ;  figs.  3,  4,  and  5,  usual  type  of  distrilmtive  hyph;e  found  in  swollen  branches 
in  the  cortical  parenchyma  and  medulla;  figs.  6,  7,  8,  and  9,  fruiting  hyphie,  show- 
ing successive  stages  in  the  development  of  ascogenous  cells  from  the  su})cuticular 
mycelium  (6)  to  the  half-formed  ascogenous  cells  (9).  (See  PI.  Ill  for  further  stages 
in  the  development  of  the  ascogenous  cells  and  asci.) 


THE  MYCELIUM  OF  THE  FUNGUS.  35 

tlio  vegetative  hyphpe,  which  are  usually  found  somewhat  later  among 
tiu>  cells  of  the  spongy  pariMichyma,  below  the  vascular  network.  The 
loss  of  chlorophyll  from  the  two  classes  of  leaf  parenchyma  couunonly 
jn-eserves  the  order  here  given.  The  form  of  the  vegetative  hyphjc  is 
very  irregular,  and  their  elements,  or  cell  members,  are  often  of  dif- 
ferent size,  length,  and  shape.  The  cells  vary  greatly  in  diameter 
from  one  end  to  the  other,  are  frequently  much  curved  and  twisted, 
and  oftentimes  appear  triangular  in  cross  section.  The  branches 
n..iy  arise  froui  greatly  enlarged  triangular  bifurcations,  or  in  other 
instances  directly  from  the  sides  of  the  cells.  These  vegetative  hyphiB 
are  all  intercellular  so  far  as  observed,  but  are  commonly  found  adher- 
ing closely  to  the  cell  walls  of  the  host,  frequently  wrapping  about  the 
parenchyma  cells.  The  walls  of  the  hyphee  are  semitransparent  but 
tirm,  couunonly  having  a  slight  yellowish  cast.  The  septa  present 
peculiar  characters.  Two  adjoining  cells  of  a  hypha  have  the  appear- 
ance of  being  separately  closed  at  the  end  and  united  with  each  other 
l)y  means  of  an  intervening  plate,  which  if  it  should  be  dissolved  or 
lost  would  leave  the  cells  separated  but  closed.  These  peculiar  septa  are 
remarkably  refractive  and  characteristic.  They  are  well  shown  in  the 
drawings  of  Sadebeck  (Die  parasitischen  Exoasceen,  Haml)urg,  1893, 
Tab.  II,  tigs.  7,  8).  The  predominating  characters  of  the  vegetative 
hyphffi  are  shown  in  PI.  II,  tigs.  1  and  2,  of  this  bulletin.  The  hyphse 
there  shown  were  carefully  sepai-ated  from  the  leaf  parenchyma  and 
drawn  under  the  camera.  The  vegetative  hypha3  of  the  ))ranch  are 
nuich  like  those  of  the  leaf,  and  have  been  seen  most  commonly  among 
the  looser  parenchyma  cells  of  the  cortex  just  exterior  to  the  bast  fiber 
bundles.  Thus  far  they  have  never  been  found  by  the  writer  in  the 
cambial  tissues.  Sadebeck  states  that  the  mycelium  has  been  found  in 
the  pith  and  medullary  rays. 

The  distributive  hyphse  are  shown  in  PI.  II,  tigs.  3,  4,  and  5. 
They  have  been  found  by  the  writer  in  the  tissue  lying  close  beneath 
the  epidermal  cells  of  diseased  peach  twigs,  and  in  great  al)undance  in 
the  pith.  They  are  occasionally  found  in  groups  of  several  hyphffi  but 
slightly  separated  from  each  other  and  following  a  course  parallel  to 
the  longitudinal  axis  of  the  shoot.  The  cells  composing  these  hyphte 
are  much  longer  than  either  the  vegetative  or  the  fruiting  forms,  while 
they  are  nearh'  straight  and  of  more  uniform  diameter.  The  septa 
are  characteristic  of  those  found  in  the  other  forms  of  the  mycelium 
of  this  fungus.  Such  distributive  hyphie  have  been  follow^ed  for  some 
little  distance  in  the  swollen  portions  of  the  peach  twig,  and  the  name 
has  been  given  them  from  their  apparent  function  of  spreading  the 
fungus  in  the  branch.  Such  hyphie  ])ranch  l)y  })ifurcation,  the  branches 
commonly  assuming  a  course  parallel  to  the  parent  hypha  and  the 
direction  of  the  peach  limb. 


36     PEACH  LEAF  CUEL:  ITS  NATURE  AND  TREATMENT. 

The  fruiting  hypha?  have  been  seen  to  arise  in  Exoascus  deformmis 
from  the  vegetative  hyphte  after  the  latter  have  become  well  developed 
in  the  parenchj^ma  of  the  leaf.  Large,  well-nourished  vegetative 
hj'phse  commonly  develop  just  below  the  epidermal  cells  of  the  upper 
leaf  surface/  From  these  hyphre  arise  branches  which  penetrate 
between  the  cells  of  the  epidermis,  and  press  themselves  between  the 
epidermis  and  the  cuticle.  Such  hyphas  may  be  seen  both  in  section 
and  surface  view.  These  subcuticular  hyphje  now  branch  freely,  and 
follow  with  more  or  less  regularity  the  triangular  space  formed  by  the 
juncture  of  two  adjoining  and  somewhat  rounded  epidermal  cells  with 
the  cuticle.  This  is  presumably  the  line  of  least  resistance  to  the 
advance  of  the  hyph^.  By  opening  and  following  these  channels  the 
mycelium  assumes  the  outlines  of  a  quite  uniform  network  beneath  the 
cuticle.  While  this  manner  of  following  the  line  of  juncture  of  adjoin- 
ing epidermal  cells  with  the  cuticle  is  common,  it  is  not  invariably  the 
practice  of  the  fungus,  cases  occurring  where  apparently  no  such 
agreement  exists.  Series  of  straight  and  parallel  hyphse,  at  regular 
distances  apart,  are  sometimes  met  with  beneath  the  cuticle  as  the 
precursors  of  the  hymenial  layer.  These  send  off  lateral  branches  on 
either  side,  which  hy  enlarging,  l)ranching,  and  curving  eventually 
occupy  most  of  the  surface  of  the  epidermis  between  the  main  hyphre. 
It  is  probable  that  the  path  followed  b}'  the  first  subcuticular  hyphse 
depends  largely  upon  the  firmness  with  which  the  cuticle  is  attached 
to  the  epidermal  cells,  and  which  may  largely  depend  upon  the  amount 
of  water  in  the  tissues  and  upon  the  age  and  rapidity  of  their  growth. 
With  the  leaf  tissues  full  of  water  and  making  a  rapid  growth,  the 
hyphfc  could  naturally  pursue  a  more  direct  course  beneath  the  cuti- 
cle than  under  contrary  conditions.  After  the  establishment  of  a 
much-branched  filamentous  network  of  subcuticular  h3^pha%  the  cells 
of  which  are  usually  slender,  of  medium  length,  thin-walled,  and  of 
comparatively  uniform  diameter  (PI.  II,  fig.  6),  these  cells  begin  to 
distend,  and  are  shortened  by  the  formation  of  new  transverse  septa 
(PI.  II,  fig.  7,  and  PL  III,  fig.  22).  A])out  this  time  all  septa  become 
nuich  more  distinct.  At  a  later  stage  the  cells  become  still  more 
distended  and  subspherical  (PI.   II,  fig.  8).     As  these  enlarged  cells 

^  Miss  E.  L.  Knowles  (Bot.  Gaz.,  Vol.  XII,  No.  9,  p.  217)  has  called  atten- 
tion to  the  fact  that  Winter's  statement  that  "the  asci  break  through  the  lower 
side  of  the  leaf"  does  not  hold  good  for  the  peach  (Kryp.  Flora,  Asco.,  p.  6,  and 
Krank.  Kultur-Gewiichse,  Leipzig,  1878,  p.  47) .  Winter  is  not  alone  in  stating  that 
the  asci  of  E.  deformans  arise  on  the  under  surface  of  the  leaves.  Robinson  says:  "  The 
asci  are  borne  on  both  sides  of  the  leaf,  but  in  greater  numbers  upon  the  lower  sur- 
face" (Robinson,  B.  L.,  Notes  on  the  Genus  Taphrina,  Ann.  Bot.,  Nov.,  1887,  Vol.  I, 
No.  11,  p.  168) .  Atkinson  also  says:  "The  asci  are  developed  on  both  surfaces  of  the 
leaf"  (Atkinson,  Geo.  F.,  Leaf  Curl  and  Plum  Pockets,  Cornell  Agr.  Exp.  Sta.  Bull. 
No.  73,  1894,  p.  325) .  These  and  other  like  statements  have  probably  arisen  from  a 
study  of  other  foliage  than  that  of  the  peach,  and  of  other  species  of  Exoascus,  and 
qave  been  perpetuated  through  insufficient  reference  to  nature. 


I 


DESCRIPTION  OF  PLATE  III. 

Fruitinii  s^ta.ijri'.';  of  Exoascns  deformans.  Figs.  1  to  13  (600/1),  various  stages  and 
conditions  of  tlie  asci  and  ascospores  of  tlie  fungus.  Fig.  14,  section  of  peach  leaf, 
showing  subepidermal  and  subcuticular  mycelium,  the  latter  already  partially  dif- 
ferentiated into  ascogenous  cell.s.  Fig.  15,  section  of  peach  leaf  showing  three  suc- 
cessive stages  in  the  formation  of  the  asci  from  the  ascogenous  cells:  a,  the  pushing 
of  the  ascogenous  cells;  b,  the  ascus  nearly  full-formed,  but  with  the  contents  still 
connected  with  the  ascogenous  cell;  c,  the  asci  separated  by  ivsei^tum  from  the  ascog- 
enous cell,  which  now  forms  the  stalk  cell  of  the  ascus.  Figs.  16  to  20  (600/1) ,  thi* 
first  stages  in  the  formation  of  the  asci  from  the  ascogenous  cells,  the  latter  being 
ruptured  above  and  the  asci  pushing  upward.  "  i\,  the  pr.shing  of  a  forming 
ascus  through  the  leaf  cuticle  (600/1).     Figs.  22'  ^600/1),  v^arious  stages  in  the 

formation  of  ascogenous  cells  from  subcuticular  j  um.      (For  several  early  stages 

in  this  process  see  PI.  II,  figs.  6  to  9).     Figs.  28  *  (600/1)  show  fully  developed 

ascogenous  cells  as  seen  from  above.     •  ^    "^ 

^1 


i 


,r 
at 


BULL.   20,   DIV.   VEQ.   PHYS.   &   PATH.,   U.  S.   DEPT.   AQRJCULTURE. 


FRUITING    STAGES    OF    EXOASCUS    DEFORMANS. 

A.Hu«n  A-O..Litl..  K«iliinonr. 


THE    B^RtriTlNG    HABITS    OK    THE    FUNGUS.  37 

spread  out  Ix'twccii  the  cpidcnnal  cells  of  the  leal"  and  the  cuti- 
cle they  are  nuich  distorted,  curved,  and  lohed,  the  branches  and 
lobes  eventually  tillint>\  in  a  ((uite  uniform  and  continuous  manner,  the 
entire  space  between  the  elevated  cuticii^  and  epidermis,  so  tliat  a 
more  or  less  perfect  and  continuous  hymenial  layer  of  ascogenous 
cells  is  formed  (PI.  II.  t\g.  t»:  PI.  Ill,  %s.  23,  24,  25,  2<;,  and  27).  At 
tliis  time  the  cells  become  well  rounded  and  heavy-walled,  and  they 
may  or  may  not  become  loosened  and  separated  from  each  other 
(PI.  III.  iij>s.  28-30).  These  are  now  the  fully  developed  ascog-c- 
nous  cells  of  the  hymenium,  and  they  are  fully  stored  with  nutritive 
materials  for  the  development  of  the  asci.  In  their  compact,  continu- 
ous, and  rounded  condition  they  resemble,  when  viewed  from  the  sur- 
face, the  stones  in  the  pavement  of  an  old  Roman  highway. 

The  various  phases  of  the  development  of  the  hymenium  of  ascog- 
enous  cells  may  often  be  observed  at  one  time  in  a  single  infected 
leaf.  The  center  of  a  swollen  spot  frequently  shows  the  fully  devel- 
oped h3'meniuni,  while  at  the  margin  of  the  spot  the  first  filamentous 
hyphtv  are  just  spreading  beneath  the  cuticle.  In  such  instances 
nearly  all  stages  in  the  development  of  the  ascogenous  cells  ma}^  be 
studied  in  a  single  well-prepared  specimen.  The  development  of  a 
subcuticular  hymenium  has  been  observed  in  the  petiole  as  well  as  in 
the  ])ladt^  of  th(>  leaf. 

The  formation  of  the  asci  from  the  fully  developed  ascogenous  cells 
has  bt^en  carefully  followed  in  the  stud}^  of  a  large  number  of  prepara- 
tions. Thus  far  no  sexual  phenomena  have  been  observed  in  connec- 
tion with  the  formation  of  the  ascogenous  cells  or  with  the  develop- 
ment of  the  asci.  As  already  said,  the  walls  of  the  ascogenous  cells 
are  heav}'.  The  earh'  steps  in  the  development  of  the  asci  from  these 
cells  (the  development  of  a  papilla-like  elevation  on  the  upper  surface 
of  the  cells)  cause  the  rupture  or  dissolution  of  the  heavy  wall  where 
the  elevation  occurs.  The  phenomenon  is  that  of  the  germination  of 
a  heavy-walled  spore,  or,  perhaps,  more  properly,  the  outgrowth  or 
prolongation  of  an  endospore  through  the  rupture  of  the  epispore 
(PI.  Ill,  tigs.  17.  18.  etc.).  The  fact  to  be  noted  is  the  perfect  rest- 
ing condition  into  which  the  ascogenous  cells  may  pass  before  the 
development  of  the  ascus,  as  shown  by  the  marked  delimitation  between 
the  thin  wall  of  the  forming  ascus  and  the  heavy  wall  of  the  ascogenous 
cell.  The  entire  isolation  of  single  ascogenous  cells  or  groups  of  cells 
from  all  sources  of  vegetiitive  supply  indicates  that  the  ascus  is 
entirely  dependent  for  its  nourishiuent  upon  the  stored  materials  of 
the  cell  from  which  it  arises.  The  ])ushing  of  the  ascus  after  the  com- 
plete development  of  the  ascogenous  cell  instead  of  in  direct  con- 
tinuation of  the  development  of  the  latter,  also  ])oints  to  a  probal)le 
cessation  and  renewal  of  the  reproductive  activity  of  the  ascogenous 
cell. 


38     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

J II  view  of  these  facts,  it  seems  possil^le  that  the  asoogenous  cells 
may  be  capable  of  enduring,  under  especially  favorable  conditions,  a 
resting  period  of  considerable  time.  Such  resting  ascogenous  cells 
have  ])een  sought  for  upon  the  swollen  branches  of  the  peach,  how- 
ever, without  success.  Further  research  along  this  line  is  desirable. 
As  the  fungus  is  already  known  to  fruit  upon  the  blade  and  petiole 
of  the  leaf  and  upon  the  blossom,  and  a  vegetative  mycelium  is  found 
growing  thriftily  in  the  swollen  branches,  there  seems  to  be  no  good 
reason  why  the  parasite  may  not  fruit  upon  the  infected  twigs. 

The  perpendicular  growth  of  the  developing  asci  in  the  leaf  soon  rup- 
tures or  pierces  the  cuticle,  and  where  large  numbers  of  asci  develop 
at  the  same  time  the  cuticle  is  lifted,  torn,  and  lost,  the  asci  forming 
a  more  or  less  continuous  plush-like  surface  growth.  Isolated  asci 
press  through  the  cuticle  so  as  to  form  separate  perforations  (PI.  Ill, 
fig.  21).  The  contents  of  the  forming  ascus  are  finely  granular,  and 
as  the  ascus  elongates  these  contents  crowd  into  the  upper  portion  and 
a  septum  is  formed  across  the  basal  part  in  such  a  manner  as  to  cut  off 
the  now  emptied  ascogenous  cell  as  a  stalk  cell  for  the  ascus  (PI.  Ill, 
fig.  15).  When  fully  developed  the  asci  are  usually  broader  at  the  top 
than  at  the  base,  and  often  somewhat  clavato  in  form.  A  series  of  asci 
measured  varied  in  length  from  34  to  -11:  yw,  the  average  being  38  // ;  the 
width  of  the  asci  ranged  from  10  to  12  yu,  and  the  height  of  the  stalk 
cells  varied  from  S  to  13  yw,  the  average  being  slightly  over  10  fi  (PI. 
Ill,  figs.  1-13). 

The  formation  of  the  ascospores  in  Exoascus  deformans  has  not  ])een 
carefully  studied  ])y  the  writer.  Sadebeck  has  shown,  however,  for  7i'. 
turgidus^  that  mitotic  nuclear  division  occurs  in  the  ascus  in  connec- 
tion with  spore  formation  (Untersuch.  iiber  die  Pilzgattung  Exoas- 
cus, Hamburg,  1881,  PI.  Ill,  fig.  20).  The  ascospores  developed  in 
the  asci  of  E.  defonaanx  vary  in  numl^er  from  3  to  8,  the  latter  being 
the  full  and  typical  number.  When  mature  they  are  surrounded  by  a 
moderately  firm  cellulose  wall,  which  is  rather  inconspicuous,  owing 
to  its  transparency.  The  spores  are  usually  somewhat  oval  in  foriu, 
being  longer  than  broad,  l)ut  occasionally  some  are  seen  which  appear 
nearly  or  quite  spherical.  Fresh  ascospores  sometimes  show  distinct 
nuclear  phenomena.  This  has  been  observed  with  spores  still  within 
the  ascus,  as  well  as  in  many  which  have  escaped.  The  nucleated 
appearance  seems  less  common  in  budding  or  germinating  ascospores 
than  in  those  in  a  resting  condition  (PL  IV,  figs.  1,  2,  3,  4,  and  10). 
The  average  length  of  the  ascospores  measured  was  Tjy  yw,  the  length 
varying  from  6  to  9  yw,  and  the  average  width  was  (iyV  A*-  varying  from 
5  to  7  yu.  The  ascospores  escape  from  the  ascus  through  an  apical  rup- 
ture of  the  latter. 

Germination  of  the  ascospores  has  been  observed  by  the  writer  to 
proceed  in  two  ways:  (1)  By  means  of  })udding  oi-  conidia  formation; 
(2)  by  means  of  stocky  germ  tubes,  often  one  branched  and  reseml)ling 
promycelia. 


DESCRIPTION  OF  PLATE  IV. 

Germination  of  the  ascospores  and  conidia  of  Exoaseus  deformans.  Figs.  1  to  12 
(about  800/1) ,  ascospores,  of  which  five  show  nuclear  phenomena  and  several  are 
budding.  Figs.  13  to  21  (800/1) ,  thin-walled  conidia,  several  of  which  are  producing 
buds;  the  remaining  spores,  unnumbered,  show  various  modes  of  promycelium 
formation  or  mycelial  germination. 


BULL.  20,  DIV.  VEG.  PHYS.  &  PATH.,  U.  S.  DEPT.  AGRICULTURE. 


PLATE   IV. 


Nevffoii  H.  Ileicr    Hfl  Tial    ()n| 


GERMINATION  OF  THE  SPORES  OF  EXOASCUS  DEFORMANS. 

A.lloeii  lb  t'M.  Uth.  Bulli>i,>ir<.. 


GERMINATION    OF    THE    SPORES.  39 

Budding-  of  the  ascospores  occurs  either  before  or  after  the  escape 
of  the  spores  from  the  ascus.  In  the  formation  of  the  bud  conidia  the 
process  may  take  place  from  the  ascospore  direct,  one  conidium  after 
another  being  produced,  or  the  contents  of  the  ascospore  may  pass  into 
a  thin-walled  conidium  nearly  or  (^uite  equal  in  size  to  the  ascospore, 
this  large  conidium  then  assuming  the  function  of  Inid  production. 
Ordinarily  the  ascospore  buds  at  one  point  only,  but  ))ud  formation  at 
two  points  has  been  seen.  Budding  occurs  most  commonly  at  one  end 
of  the  ascospore,  but  occasionally  lateral  buds  are  observed.  In  the 
early  stages  of  Inidding  the  ascospore  sometimes  shows  a  nipple-like 
swelling  at  one  end,  reminding  one  of  the  germinating  end  of  the 
sporangium  in  the  Peronosporece.  The  successive  primary  conidia  bud- 
ding from  an  ascospore  may  become  loosened  and  turned  to  one  side 
by  the  following  conidium,  which  swells  from  the  same  germ  pore  of 
the  ascospore.  In  other  cases  several  conidia  may  remain  united  with 
each  other,  but  when  this  condition  is  observed  it  is  frequently  the 
result  of  the  secondary  or  tertiary  budding  of  the  primary  conidium, 
several  orders  or  generations  of  buds  remaining  united.  When  the 
process  of  primary  conidial  budding-  can  no  longer  take  place  the  empty 
ascospore  may  or  may  not  become  separated  from  the  last  primary 
conidium.  With  the  exception  of  the  case  above  referred  to,  the  dif- 
ferent orders  or  series  of  conidia  (primary,  secondary,  tertiary,  etc.) 
when  grown  in  pure  water,  are  each  smaller  than  the  preceding,  and 
the  conidia  are  considerably  elongated  in  form,  sometimes  almost 
cylindrical.  The  walls  of  the  conidia  are  more  delicate  than  those  of 
the  parent  spore.  In  a  suitable  nourishing  fluid,  as  the  extract  of  malt, 
the  conidia  take  up  nourishment  and  increase  in  size,  thus  enabling 
them  to  continue  the  budding  process  for  considerable  periods  of  time, 
as  in  the  yeasts  (Saccharomyces).  Whether  the  conidia  of  Exoascus 
deftmnans  are  able  to  induce  an  alcoholic  fermentation  through  their 
growth  in  saccharine  culture  media  is  not  known,  but  Sadebeck  states 
that  the  conidia  of  other  species  of  this  genus  certainly  possess  this 
fermenting  power. 

The  second  method  of  germination  of  the  ascospore  of  Exoascus 
deformans,  that  is,  the  pushing  of  germ  tubes,  is  rarely  met  with 
except  upon  the  host  plant  itself.  Such  mode  of  germination  is  shown 
in  PI.  IV.  The  germ  tu]>e  produced  from  the  ascospore  is  usuallv 
much  swollen  near  the  spore  and  tapers  considerably  toward  the 
extremity,  though  not  infrequently  considerable  constrictions  occur 
at  one  or  more  points  in  its  course.  It  seems  probable  that  this  tube  is 
in  many  cases  capable  of  directly  infecting  the  host,  probably  through 
a  stoma,  as  observed  by  Sadebeck  in  Exoamus  tosquinetii^  and  that  its 
function  is  not  wholly  the  abjointing  of  sporidia.  Such  separation  of 
sporidia,  in  fact,  has  not  thus  far  been  observed.  The  germ  tube, 
or  promycelium,  is  connected  with  the  spore  by  a  very  narrow  and 
short  tube,  with  straight  and  })arallel  walls.  The  same  mode  of  con- 
nection is  also  observable  in  the  formation  of  the  bud  conidia,  and 


40  PEACH    LEAF    OFRL:    ITS    NATURE    AND    TREATMENT.    " 

reminds  one  of  the  sterigmata  bearing  the  sporangia  of  PhytophtJiora 
mfeatans. 

Thus  far  efforts  to  induce  filamentous  germination  of  the  liud  conidia 
or  of  the  ascospores  of  Exoaseits  deformans  in  culture  media  have 
proved  unsuccessful.  Brefeld  has  worked  with  this  problem  for 
months,  and  the  writer  has  frequently  attempted  to  obtain  this  form 
of  germination. '  Budding  occurs,  as  already  indicated,  quite  readily 
in  various  nutrient  solutions,  and  short  promycelia  from  the  ascospores 
have  l)een  found  in  some  cultures.  In  nearly  if  not  all  cases,  however, 
the  ascospores  showing  promycelia  or  short  mycelial  germination  have 
shown  that  this  germination  occurred  under  natural  conditions  upon 
the  peach  leaf,  the  germinated  spores  l^eing  transferred  from  the  leaf 
to  the  culture  in  preparing  the  latter.  It  may  be  added  here  that  the 
bud  conidia  are  also  formed  in  vast  numbers  upon  the  surface  of  the 
infested  leaf  after  the  maturing  of  the  ascospores.  It  is  largely  these 
conidia  which  give  the  infested  leaf  the  marked  white  appearance 
conmionly  observed  at  the  height  of  the  disease.  The  leaf  appears  as 
if  covered  with  flour  or  a  heavy  white  bloom. 

RELATIONS   OF   THE    FUNGUS   TO    THE    HOST. 

Under  a  previous  heading  in  this  chapter  the  physical  condition? 
which  influence  the  serious  development  of  peach  leaf  curl  have  ])een 
considered  in  accordance  with  the  light  which  we  now  have  relative  to 
such  influences,  and  there  remain  to  l>e  taken  up  at  this  time  the  more 
intimate  and  direct  relations  of  the  host  and  parasite.  These  relations 
include  the  action  of  the  fungus  upon  the  cell  contents,  the  cell  walls, 
and  the  cellular  tissues  of  the  host:  the  probable  mode  of  infection  and 
the  spread  of  the  parasite  within  the  tissues;  the  wintering  of  the 
fungus  upon  the  tree;  etc. 

'A  very  considerable  number  of  cultural  experiments  have  been  tried.  The  cul- 
tures of  ascospores  and  conidia  have  been  subjected  to  temperatures  much  below  the 
freezing  point  and  to  various  degrees  of  heat  in  the  thermostat.  Sudden  changes  of 
temperature  have  been  tried.  Increased  antl  diminished  amounts  of  oxygen,  as  con- 
trasted with  that  of  the  normal  atmosphere,  have  been  tested.  Even  a  chamber  filled 
with  nearly  pure  oxygen  has  produced  no  apparent  effect.  Water  from  various 
sources,  such  as  rain  water,  dew,  ice  water,  distilled  water,  tap  water,  etc.,  has  been 
tested.  Solutions  of  the  various  sugars,  malt  extract,  sterilized  beer,  plum  extract, 
etc.,  were  tried.  Hanging  drop  cultures  of  various  nutrient  media  and  plate  cultures 
of  potato-peptone-sugar  gelatin  have  not  shown  germination.  Drops  of  variou- 
nutrient  solutions  placed  upon  newly  forming  leaves  dissected  from  unopened  peach 
buds  and  these  held  in  moist  chambers  have  given  only  negative  results.  The  same 
is  true  for  peach  pits  brought  near  to  germination  and  the  cotyledons  treated  with  a 
weak  solution  of  diastase,  the  spores  ])laced  between  them  and  held  at  various  tem- 
peratures in  uioist  chambers.  Sections  of  such  cotyledons  with  spores  placed  upon 
them  were  also  prepared  in  moist  chambers.  A  brief  treatment  of  the  spores  with 
ether  was  tested  without  bringing  about  germination. 

Prillieux  states  that  attempts  to  artificially  infect  the  leaves  or  shoots  have  not 
thus  far  succeeded  (Mai.  d.  Piantes  Agr.,  Vol.  I,  p.  399). 


RELATION!^    OK    THE    FLTN(Jrs    To     TlIK    HOST,  41 

As  already  i  ndicatct  I.  (  he  writ  crs  work  wit  li  sprays  seemed  to  show  t  lial 
not  more  than  a  small  i)ereeiitaiie  of  each  yeai's  iiit'eetioiis  ordiiiai-ily 
arise  from  a  perennial  mycelium.  In  the  LoncII  oichaid.  where  the 
personally  eondueted  work  w;is  can-ied  out.  it  would  appeal-  that  not 
to  exceed  2  to  3  per  cent  of  tiie  infections  could  have  arisen  from  that 
cause.  On  the  other  hand  it  would  seen)  that  at  least  t>5  per  c«Mit  of 
the  infections  arose  from  spores,  for,  as  already  stated,  95  to  !>8  per 
cent  of  the  spring  infections  could  be  pn>vented  ))y  a  sinole  spraying-, 
and  this  was  actually  accomplished  where  the  spra^'ing-  was  done  with 
sufficient  thoroughness.  It  is  believed  by  the  writer,  howev(M-.  that 
these  percentages  will  vary  within  mod(M'at(»  limits  in  diti'erent  locali- 
ties, with  different  varieties,  and  in  different  seasons.  Tiie  following 
observations  will  explain  these  views. 

The  mycelium  of  diseased  leaves  is  found  to  l)e  connected  through 
the  leaf  petiole  with  the  mycelium  of  the  infected  limb.  From  the 
writings  of  Sadebeck  and  man}"  others  it  might  be  supposed  that  the 
leaves  were  infected  from  the  perennial  mycelium  in  a  majority  of 
eases,  and  that  the  mycelium  met  with  in  the  petiole  of  the  leaf  origi- 
nated from  the  perennial  mycelium  of  the  branch.  That  such  spring 
infection  really  occurs  from  the  wintering-  myc(dium  of  the  ])ranch 
should  perhaps  be  admitted,  but  that  such  is  the  connnon  mode  of 
infection  of  the  leaves  is  certainly  doubtful.  The  writer's  studies  have 
shown  that  the  mycelium  in  the  branch  close  to  a  clustcn-  of  infected 
leaves  diminishes  in  amount  as  it  passes  upward  or  downward  in  the 
branch  from  such  leaves.  This  fact  is  as  obvious  from  microscopic 
studies  of  the  infested  tissues  as  from  the  external  hypertrophies 
observable  to  the  eye.  A  macroscopic  examination  of  diseased  and 
swollen  branches  will  show  that  the  enlarged  parts  may  extend  upward 
or  downward  along  the  branch  from  the  base  of  th(^  petioles  of  the 
leaves,  which  seem  to  represent  the  center  of  infection.  In  a  majorit}' 
of  cases  these  swollen  ridges  terminate  before  reaching  another  leaf 
bud,  though  in  some  instances  they  are  seen  to  extend  along  the  branch 
throughout  the  entire  length  of  one  or  more  internodes,  and  in  such 
cases  it  is  fair  to  suppose  that  the  mycelium  ma^^  have  infected  the 
young  leaA'es  of  a  second  or  third  bud  in  its  course.  It  should  be 
remembered,  however,  that  this  mycelium,  in  a  great  majority  of 
instances,  indicates  no  connection  with  a  previous  year's  mycelial 
growth,  but  has  evidently  just  entered  the  l)ranch  from  one  or  more 
infected  leaves.  The  microscopic  evidence  supports  these  conclusions, 
which  are,  to  some  extent,  in  harmony  with  Benton's  observations,  to 
be  hereinafter  consid(M-ed,  l)ut  th(^  writer  is  scarcely  prepared  to  admit 
the  large  percentage  of  spring  infections  arising  from  now  mycelium 
entering  the  branch  which  the  observations  of  that  writin-  seem  to 
imply.*     The  microscope  shows  that  the  hj'pha?  which  })ass  away  from 

'Pacific  Kural  I'rcss,  Auir.  L',  iSitO,  p.  SS. 


42     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

the  Inisc  nH  the  k'uf  petiole  i^mdiialh"  decrease  in  numbers  as  they 
recede  from  the  leaves,  and  they  appear  to  l)e  wholly  lost  at  a  short 
distance  from  the  point  of  entrance  into  the  shoot.  As  a  rule,  little  or 
no  mycelium  has  been  found  extendinjj- more  than  1  or  2  inches  1)eyond 
a  point  where  external  macroscopic  evidence  of  disease  exists. 

The  preceding  facts  lead  to  the  'oelief  that  where  mycelial  infection 
of  f<)liag(;  takes  place  from  the  branch  it  is  usually  done  in  the  spring 
from  hyphte  arising  from  spore-infected  leaves  of  the  same  season, 
and  that  this  occurs  only  in  comparatively  few  instances  or  in  bad 
cases  of  disease.  The}^  also  indicate  that  living  perennial  nwcelium 
which  succeeds  in  accomplishing  spring  infection,  is  comparatively 
rare.  Badly  infested  and  swollen  branches  are  apt  to  die  and  dry  out, 
thus  att'ording  no  living  tissue  for  the  support  of  the  infesting  myce- 
lium. Such  l)ranches,  even  if  living  until  the  following  spring,  are 
not  apt  to  produce  much  growth,  and  frequently  produce  none  what- 
ever. Furthermore,  the  badly  swollen  mycelium-infested  branches 
are  comparatively  few,  and  it  is  believed  that  the  infested  winter  buds 
of  these  branches  very  rarely  exceed  2  to  3  per  cent  of  the  total  mmi- 
ber  of  buds  upon  the  tree.  Most  branches  appear  to  sutler  from  the 
disease  only  in  an  indirect  manner,  that  is,  by  the  fall  of  affected 
foliage.  It  seems  probable  to  the  writer,  therefore,  that  the  swollen 
branches,  in  which  the  swelling  is  apparent  to  the  eye,  constitute  the 
true  and  almost  exclusive  home  of  the  perennial  mycelium,  and  there- 
fore supply  the  only  possible  source  of  spring  infection  by  the  win- 
tering h^'phjp,  and  conseqitentlv  the  only  source  of  infection  not 
controllable  by  spraj's.  This  is  in  harmony  with  the  results  of  wide- 
spread orchard  treatment.  All  but  2  to  3  per  cent  of  infections  have 
been  prevented  by  a  single  spraying.  (See  the  results  of  work  on 
half-spraj'^ed  trees.)  That  such  spraying  did  not  prevent  the  spread 
of  the  mycelium  in  the  inner  tissues  of  the  host  is  shown  by  the  fact 
that  when  it  is  delayed  until  the  leaves  have  fairly  started  and  have 
become  infested,  the  treatment  is  ineffective  and  the  disease  will  con- 
tinue to  develop  and  both  foliage  and  crop  may  be  lost.  It  is  not  the 
checking  of  the  spread  of  the  mycelium  from  the  branch  to  the  new 
leaves,  therefore,  that  results  from  spraying,  but  the  prevention  of  the 
early  spore  infections  from  withotit;  and  as  all  but  2  to  3  per  cent  of 
the  3^ear's  infections  may  be  thus  prevented,  all  of  such  infections 
must  be  considered  as  arising  from  spores. 

The  limitation  of  the  perennial  mycelium  of  Exoasciis  deformanx:  io 
the  swollen  branches  or  branch  parts,  as  here  held,  is  in  harmony  with 
observed  facts  respecting  other  species  of  Exoascece.  It  is  not  under- 
stood, for  instance,  that  trees  developing  witches'  brooms  are  infested 
in  all  their  branches,  but  that  the  branch-infesting  mycelium  is  limited 
in  its  distribution  to  those  centers  which  develop  the  abnormal  nudti- 
plication  of  shoots,  the  swellings  and  other  external  manifestations 
of  disease.     (See  Pis.  I,  V,  and  VI,  and  descriptions,  in  connection  with 


DESCRIPTION  OF  PLATE  V. 

Terminal  peach  twigs  badly  affected  by  curl.  The  mycelium  of  the  fungus  has 
entered  the  growing  end  of  these  shoots,  and  the  conditions  being  favorable,  it  has 
developed  to  such  an  extent  as  to  prevent  further  elongation  of  the  twig,  thus  form- 
ing a  compact  head,  with  greatly  shortened  internodes.  It  is  in  shoots  of  this  char- 
acter that  the  mycelium  is  found,  and  its  extent  is  nearly  coincident,  so  far  as 
observed,  with  the  swollen  portions  of  the  branch.  Such  swollen  branches  consti- 
tute a  striking  feature  of  the  disease,  but  rarely  involve  more  than  2  to  3  per  cent  of 
the  buds  of  a  tree.  Specimens  were  collected  at  Santa  Ana  in  the  spring  of  1899  and 
photographed  natural  size.      (Compare  with  Pis.  I  and  VI.) 


Bull    20,  Div,  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  V. 


Peach  Twigs  and  Leaves  Affected  by  Curl. 

The  (li.stril)Utivu  niyceliuin  of  the  I'uii^riis  is  I'dunil  in  such  swulleu  tinmclies. 


DESCRIPTION  OF  PLATE  Xl. 

Sprayed  and  iinsprayed  branches  of  Lovell  peach  trees  in  the  experiment  ]>lock  at 
Biggs,  as  they  appeared  in  1895.  The  sprayed  branches  at  the  left  show  the  large 
amount  of  fruit  and  healthy  foliage  on  the  s])rayed  trees;  the  unsprayed  branches 
at  the  right  have  lost  most  of  their  foliage  and  all  the  fruit  from  curl.  These 
unsprayed  Ijranches  show  the  typical  ami  common  effects  of  curl.  Hypertrophy  of 
the  branch  is  not  shown,  and  it  is  probal)le  that  these  branches  carry  little  if  any 
perennial  mycelium.  Thorough  winter  treatment  of  such  branches  with  proper 
fungicides  will  prevent  98  per  cent  of  the  spring  infections  and  conduce  to  the 
development  of  foliage  and  fruit,  as  shown  on  the  branches  at  the  left.  All  these 
trees  were  equally  infected  by  the  fungus  in  1893,  when  the  orchard  suffered  severely 
from  curl,  and  had  the  l^rancrhes  at  the  left  not  been  sprayed  before  the  leaf  buds 
opened  in  the  spring  of  1895,  they  would  have  been  in  the  same  condition  as  those 
at  the  right  nf  the  j.lat*".      (Compare  with  Pis.  I,  V,  and  VII.) 


Buil.  20.  Div.  Veg.  Phys.  &i  Path.,  U.  S.  Dept.  at  Agriculture. 


Plate  VI. 


CONCLUSIONS    REGARDING    SPRING    INFECTIONS.  43 

tlu^  l)rosont  ivniarks  on  intVsttMl  and  noiiinfostod  hnuichcs, )  It  soonis 
[)r()lnil)lo,  thorot'oro,  (1)  that  most  of  thespriiio- intVctioiisof  the  pcju-h 
oc't'ur  from  spores  which  have  wintered  on  th(>  tre(>andal)out  the  lu^wly 
formed  buds;  (2)  that  most  of  the  infectinl  halves  fall  off  without 
infectinj»-  the  l)raneh  whieh  bears  them;  (3)  that  the  mycelium  of  badly 
diseased  leaves  sometimes  infects  the  branch  throujrh  the  leaf  petiole; 
(-1)  that  such  mycelium  after  entering-  the  branch  may  pass  upward 
or  downward,  and  in  some  instances  may  follow  the  branch  foi-  the 
length  of  one  or  at  most  a  few  internodes,  and  possibly  infect  one 
or  two  adjoining  buds;  (5)  that  badly  infested  branches  usually  die 
during-  the  year;  while  in  comparatively  few  instances  they  may  sup- 
port a  living- mycelium  capable  of  inducing  spring-  infection  of  opening 
l)ucls;  ((>)  that  uiost  infected  branches  show  by  external  hypertrophy 
the  presence  of  the  parasite,  which  may  commonly  be  removed  by 
pruning-  ott'  the  hypertrophied  parts  at  a  point  a  few  inches  below 
the  swelling;  (7)  that  seasons,  atmospheric  conditions,  localities,  and 
varieties  ma}^  have  a  limited  bearing  on  the  extension  of  the  mycelium 
in  the  branch  and  upon  the  amount  of  mycelium  wintering  in  an 
active  state,  although  the  results  of  spraying-  in  many  parts  of  the 
country,  continued  for  several  years,  have  shown  the  variation  in 
these  respects  to  be  confined  within  comparativelv  narrow  limits. 

The  direct  infection  of  the  peach  leaf  by  means  of  the  spores  of 
Exoaseus  deformans  has  not  been  seen.  The  efforts  made  to  observe 
the  germination  and  penetration  of  the  fungus  have  already  been 
touched  upon.  One  thing  seems  certain,  viz,  that  under  ordinary 
conditions  this  form  of  infection  occurs  at  a  very  early  period  in  the 
development  of  the  leaf,  but  evidently  not  before  the  opening  of  the 
leaf  buds.  Veiy  young  leaves  are  found  to  be  already  infected,  but 
spraying  just  before  the  buds  expand  will  prevent  this  infection,  i.  e., 
infection  may  be  prevented  by  the  treatment  of  closed  buds,  which 
would  scarcely  be  true  if  a  perennial  mycelium  were  within.  If  we 
may  judge  by  analogy,  the  germ  tube  of  the  fungus  enters  the  leaf 
through  a  stoma.  Sadebeck  reports  that  such  was  his  ol)servati()n  in 
Kroascus  tosquinetii^  in  which  species  the  germ  tube  creeps  for  a  short 
distance  on  the  leaf  surface,  and  then  enters  a  stoma,  much  as  in  the 
germination  of  the  conidium  of  PIn/tojtIithora  omnivora. 

The  major  portion  of  the  spring  infection  of  foliage  occurs  while 
the  latter  is  young  and  tender,  but  it  is  observed  that  new  infections 
may  take  place  for  a  considerable  time  if  the  various  inlluencing  con- 
ditions continue  favorable  to  the  fungus.  These  conditions  act  chieHy 
in  suddenly  retarding  the  transpiration  of  the  host,  and  some  of  them 
have  already  been  discussed.  On  the  other  hand,  a  short  period  of 
spore  infection  may  be  expected  when  external  influences  are  such 
that  transpiration  is  rapid  and  normal.  The  longer  or  shorter  course 
of  the  disease  in  spring- may  be  said  to  depend  largely,  therefore,  upon 
the  greater  or  less  susceptibility  of  the  tissues  of  the  host,  mostly 


44  PEACH    LEAF    CURL*.    ITri    NATURE    AND   TREATMENT. 

resulting'-  from  utmosplioric  iiiliiuMic-cs.  The  injuiy  wliicli  tlic  fungus 
may  do  after  infection  is  also  dependent,  where  development  of  the 
fungus  has  not  progressed  too  far,  upon  a  verj^  nice  bahince  of  the 
atniosplieric  conditions.  Newly  infected  leaves  may  be  greatly 
distorted  and  fall  at  an  early  date,  or  they  may  be  only  slightly 
injured  ])y  the  fungus,  according  to  the  atmospheric  conditions  prevail- 
ing and  their  influence  toward  softening  or  hardening  the  tissues  and 
moistening  the  intercellular  spaces  of  the  host.  A  few  days  favorable 
to  the  drying  and  toughening  of  the  parenchyma  of  the  infested  Leaf 
may  entirely  check  the  spread  of  the  fungus.  The  action  of  the 
mycelium  of  E.  deformaiis  upon  the  tissues  of  the  leaf  and  branch  of 
the  peach  has  ])een  widely  remarked.  The  hypertrophies  of  peach 
branches,  due  to  this  parasite,  are  as  striking  and  characteristic  as  are 
the  witches'  brooms  caused  on  other  hosts  by  various  ExoascecB.  In 
the  case  of  the  peach,  however,  there  is  rarely  if  ever  any  increase 
noted  in  the  number  of  shoots,  as  upon  the  cherry,  the  hypertrophy 
manifesting  Itself  in  enlargements  and  twistings  of  the  infested 
branch.  There  is  often  a  great  reduction  in  the  length  of  the  infested 
portion  of  the  shoot  and  a  shortening  of  the  internodes,  so  that  the 
approximated  and  enlarged  leaves  give  a  tufted  or  plumed  appearance 
to  the  shoot.  An  examination  of  transverse  sections  of  such  enlarged 
shoots  shows  that  the  enlargement  is  due  to  a  great  increase  in  the 
number  of  cells  of  the  cortical  parenchyma,  and  frequently  an  entire 
separation  of  such  cells  into  a  network  or  series  of  chainlike  cells. 
The  structure  of  the  infested  parenchyma  is  altered,  the  cells  being- 
enlarged  and  much  more  angular  than  normally,  while  the  thickness 
of  the  tissue  from  the  bast  libers  to  the  epidermis  is  frequently  eight 
or  ten  times  as  great  as  usual.  The  parenchyma  cells  lose  the  chloro- 
phyll and  all  matter  which  the  eye  can  detect,  becoming  quite  trans- 
parent. The  cell  walls  vary  much  more  in  thickness  than  normally, 
some  of  them  being  heavier  and  others  lighter  than  in  healthy  cells. 
Transverse  and  longitudinal  sections  of  swollen  peach  twigs  show  that 
the  pith  cells  are  greatly  injured  along  the  course  of  the  infesting 
mycelium.  The  location  of  the  mycelium  ma}^  often  be  detected  by 
treating  transverse  sections  with  Bisuiark  brown,  the  infested  medul- 
lary tissue  taking  less  stain  than  that  not  harl^oring  the  fungus.  The 
walls  of  the  healthy  cells  of  the  medulla  become  reddish  brown,  while 
those  of  the  infested  tissue  assume  scarcely  more  than  a  light  yellow 
or  yellowish  brown.  The  cells  of  the  infested  tissue  are  also  much 
more  angular  and  irregular  than  those  in  which  the  mycelium  does 
not  exist,  while  in  some  instances  the  cells  collapse. 

The  action  of  E.  deformans  on  the  tissues  of  the  peach  leaf  has  been 
considered  by  different  writers,  as  Prillieux,^  Knowles,^  and  others. 

iPrillieux,  Ed.,  Mai.  d.  Plantes  Agr.,  Vol.  II,  pp.  394-400;  also  Bull,  de  la  Soc. 
But.  de  France,  1872,  T.  XIX,  Comp.  Rend.  d'Sci.,  3,  pp.  227-230, 
^Knowlcs,  EttaL.,  Bot.  Gaz.,  1887,  Vol.  XII,  pp.  216-218,  with  piau^ 


ACTION    OF    THE    FUNGUS    ON    THE    LEAF    TISSUES.  45 

The  l)adly  intVstcd  Icavos  hci'oinc  groatly  inc roused  in  thickiie.s.s  uud 
breadth  and  the  weij^'ht  is  often  much  increased  above  the  normal,  the 
tissiu>s  l)ec()me  stifi'ened  in  a  coriaceous  or  cartihiginous  manner,  tiie 
cell  walls  become  j^reatly  thickened,  and  the  cells  becomes  more  com- 
l^ressed.  The  cells  of  the  palisade  tissue  are  increased  in  size  and 
number,  and  suft'ei-  an  entires  loss  of  chloi'opiiyll,  as  in  the  case  of  the 
cortical  parenchyma  of  the  l)ranch.  The  walls  of  the  epidermal  cells 
become  considerably  thickened  and  the  nuiltiplication  of  the  paren- 
chyma cells  on  either  side  of  the  midri))  causes  a  pronounced  gather- 
ing- and  distortion  of  these  tissues.  As  the  midrib  docs  not  elongate 
in  proportion  to  the  increased  extent  of  the  parenchyma,  it  acts  as  a 
gathering  string  passing  through  the  leaf  from  end  to  end,  and  the 
})arenchyma  becomes  folded  upon  itself.  The  increase  in  the  number 
of  cells  occurs  more  extensively  among  the  palisade  tissue  of  the  upper 
half  of  the  leaf  than  among  the  cells  of  the  spongy  parenchyma  of  the 
under  leaf  surface;  hence  the  majority  of  badly  diseased  leaves  are 
convex  above  and  concave  below,  though  this  appearance  is  often  lost 
sight  of,  owing  to  the  number  and  varietv  of  folds  which  the  leaf  l)lade 
assumes. 


CHAPTER  III. 

HISTORY  OF  THE  TREATMENT  OF  PEACH  LEAF  CURL. 
THE  EUROPEAN  SITUATION. 

That  the  present  outline  of  the  gradual  development  of  methods  for 
the  treatment  of  peach  leaf  curl  in  the  United  States  may  be  properly 
appreciated,  it  is  desirable  to  first  show  the  conditions  prevailing  in 
Europe  as  presented  hj  some  of  the  leading  European  writers  on  plant 
diseases.  Prillieux,  in  an  interesting  paper  on  peach  leaf  curl,  pre- 
pared in  1872,  describes  the  fungus  Exoascus  deforiuans  and  its  action 
on  the  tissues  of  its  host.^  He  states  that  the  fruiting  fungus  should 
be  looked  upon  as  the  center  of  infection,  and  that  it  is  desirable  to 
remove  the  diseased  leaves  as  thoroughly  as  possible  and  to  destroy 
them.  He  also  states  that  this  work  should  be  supplemented  by  the 
cutting  ofi'  and  burning  of  diseased  branches.  In  1878  Winter'^  stated 
that  the  only  wa^^  to  prevent  this  disease  is  to  destroy  the  fungus  by 
caref  ulh-  removing  the  affected  leaves,  and  by  protecting  the  trees  from 
rain  during  the  unfolding  of  the  leaves,  as  rain  favors  the  spread  of  the 
parasite.  The  same  year  Felix  von  Thiimen  wrote  of  Exoascus ])rxm{^ 
the  fungus  causing  plum  pockets  and  closely  related  to  Exomcim  defor- 
nuins  of  the  peach, ^  but  made  no  recommendations  for  its  treatment.  In 
1885,  however,  he  again  spoke  of  the  plum  pocket  disease  and  pointed 
out  that  it  can  not  be  removed  except  by  severe  cutting  back  of  the 
new  and  old  wood  of  the  affected  trees.*  In  1880-81  Frank,  in  the 
second  volume  of  the  first  edition  of  his  work  on  plant  diseases,  rec- 
ommends the  cutting  back  of  the  twigs  as  a  cure  for  leaf  curl,  and  the 
quick  removal  of  the  diseased  leaves  for  prevention.'^ 

In  1886  the  well-known  work  of  Sorauer  on  plant  diseases^  appeared. 
The  treatment  recommended  by  this  author  is  somewhat  similar  to 
that  recommended  by  Frank.     He  says,  in  speaking  in  a  general  way 

^Prillieux,  Ed.,  Bull,  de  la  Soc.  Bot.  de  France,  1872,  T.  XIX,  pp.  227-230. 

-  Winter,  Dr.  Georg,  Krankheiten  der  Kulturgewiu-hse,  Leipzig,  1878,  p.  47. 

^Thiimen,  Felix  von.  Die  Pilze  und  Pocken  auf  Wein  und  Obst,  Berlin,  1878,  III, 
Fungi  Pomicoli,  pp.  88,  89. 

^Thiimen,  Felix  von,  Diebekanipfungder  Pilzkrankheiten  unsererKulturgewiichse, 
Vienna,  1886,  p.  71. 

■^  Frank,  Dr.  A.  B.,  Die  Krankheiten  der  PHanzen,  Breslau,  1880-81,  Theil  II, 
p.  526. 

"  Sorauer,  Dr.  Paul,  Handbuch  der  Pflanzenkrankheiten,  second  edition,  Theil  II, 
p.  281. 

46 


HISTORY    OF    TREATMENT.  47 

of  the  Ex<)iif<cta\  that  it  lui.s  been  proved  that  the  inyc-eliuiii  winters 
over  in  the  youngest  parts  of  the  shoots  and  in  th(>  Imds,  and  he 
roconnnends  the  removal  of  isohited  slijrhtly  diseased  leaves  soon  after 
the  first  appearance  of  the  blister-like  swellings.  When  through  the 
attaek  of  a  majority  of  the  leaves  of  a  branch  it  is  shown  that  the 
mycelium  is  already  present  in  the  axial  organs,  it  is  advised  that  all 
of  the  young  wood  of  the  affected  })ranches  be  cut  off.  Hartig  de- 
scribed peach  leaf  curl  in  1889,^  and  again  in  the  Englisii  edition  of 
his  work  published  in  181>4,''  but  he  leaves  the  su])ject  without  makimr 
any  suggestions  as  to  treatment.  In  1890  Dr.  Kirchner  published 
a  work  on  plant  diseases,"  in  which  he  recommends  the  cutting  off  of 
diseased  l)ranches  for  the  control  of  the  disease.  In  1891.  Dr.  Comes, 
in  writing  of  this  disease,  states  that  no  direct  means  for  combating 
the  parasite -exists.  He  discusses  the  gathering  and  burning  of  dis- 
eased and  fall(>n  leaves,  the  cutting  back  of  inf(>cted  branches,  and  the 
application  of  cultural  methods  in  their  influence  on  the  disease.*  A 
most  excellent  work  on  plant  diseases  by  Dr.  Tubeuf  appeared  in 
1895. '  This  writer  groups  the  diseases  caused  b}^  the  ExoaacfH'  among 
those  maladies  Avhich  should  be  combated  by  the  removal  of  the 
diseased  living  plants  and  plant  parts  (pp.  86,  87).  The  second  edition 
of  Frank's  work  on  plant  diseases  appeared  in  1896,  fifteen  vears 
after  the  publication  of  the  first  edition,  but  the  same  recommenda- 
tions for  the  treatment  of  curl  are  again  made,  word  for  word."  In 
all  the  preceding  works  there  is  no  recognition  of  the  methods  of  treat- 
ment l)eing  adopted  and  discussed  in  the  United  States  and  in  Aus- 
tralia. The  recommendations  for  cutting  away  the  diseased  branches 
so  generally  presented  are  the  same  as  advanced  by  P^hrenfels  nearly 
a  century  before  for  the  control  of  mildew  of  the  peach." 

It  is  hardly  necessary  to  say  here  what  most  orchardists  have  learncHl 
by  experience,  that  is,  that  it  is  impossible  to  eliminate  the  diseas«>  by 
ordinary  cutting  back  of  the  branches,  and  that  in  tlxc  orchai'd  it  is 
equally  impracticable  to  prevent  the  disease  by  the  early  removal  of 
the  diseased  leaves. 

About  this  time  the  work  l)eing  done  on  this  disease  appears  to  have 
attracted  the  attention  of  Europeans.  In  1894,  in  his  work  on  vege- 
table parasites,  Berlese  recommends  for  this  disease  in  Italy  the  use 

'Hartig,  Dr.  Robert,  Lehrlmch  der  Baumkraiikheiten,  Berlin,  1889,  pp.   lis.  Hit. 

-Idem,  The  Diseases  of  Trees,  London,  1894,  pp.  132, 13.3. 

^Kirchner,  Dr.  Oscar,  Die  Krankheiten  nnd  Besehiidiguiijren  niisercr  laiidwirl- 
schaftlichen  Kulturpflanzen,  Stuttgart,  1890,  p.  324. 

♦Comes,  Dr.  0.,  Crittogamia  Agraria,  Naples,  1891,  Vol.  I,  pp.  167,168. 

^Tubeuf,  Dr.  Karl  Freiherr  von,  Pflanzenkrankheiten  dnrch  kryptngamc  I'ara- 
siten  verursacht,  Berlin,  1895,  pp.  86,  87,  and  184. 

^Frank,  Dr.  A.  B.,  Die  Krankheiten  der  Pflan/en,  secoinl  edition,  I'.rfsian, 
1896,  Bd.  II,  pp.  249,  250. 

"Ehrenfels,  J.  ]\I.  Ritter  von,  Ueber  die  Krankheiten  und  Verietzungen  der 
Frucht-  oder  Gartenbaume,  Breslau,  1795,  p.  225. 


48     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

of  Bordeaux  mixture  in  the  .spring,  although  he  adds,  as  if  doubting 
its  utility,  that  the  mycelium  of  the  parasite  winters  over  under  the 
cortex  of  the  branches/ 

In  France,  in  1895,  Prillieux  published  the  first  volume  of  a  work 
on  plant  diseases,  devoting  several  pages  to  the  consideration  of  peach 
leaf  curl.'  In  this  work  the  recommendations  for  treatment  appear- 
ing in  his  paper  in  1872  are  not  given,  but  instead  it  is  stated  that 
treatuionts  with  the  salts  of  copper  seem  sometimes  to  produce  good 
results  in  preventing  the  multiplication  by  spores;  but,  as  in  the  case 
of  Berlese,  he  adds,  as  if  in  doubt  of  the  value  of  such  treatments, 
that  they  are  without  effect  upon  the  perennial  mycelium  hidden  in  the 
tissues. 

By  the  year  1898  the  true  idea  of  the  preventive  treatment  of  curl 
had  been  grasped  in  Germany.  Professor  Weisz,  in  his  paper  on 
plant  diseases,^  published  that  year,  cites  the  present  method  of  con- 
trolling curl.  After  renewing  the  older  recommendations  to  cut  off 
and  burn  the  affected  twigs,  he  says  that  the  trees  should  be  sprayed 
with  copper-soda  or  copper-lime  solution  (eau  celeste  or  Bordeaux 
mixture),  the  first  time  hefore  the  buds  open.  That  these  recom- 
mendations are  not  the  results  of  work  done  by  Weisz,  however, 
appears  probable,  for  his  description  of  the  disease  is  evidently  quoted, 
as  he  falls  into  the  error  of  Winter,  Frank,  Kirchner,  and  other 
writers  in  stating*  that  the  bloom  produced  by  the  fruiting  of  the 
fungus  appears  upon  the  under  surface  of  the  leaves.  Had  he  worked 
upon  this  disease  in  the  field  he  would  not  have  been  apt  to  follow 
the  above  authors  in  their  erroneous  description  of  the  fruiting  habits 
of  the  parasite. 

DEVELOPMENT   OF   THE    PRESENT   METHODS    OF   TREATMENT. 

The  successful  treatment  of  peach  leaf  curl  dates  from  the  time 
when  fungicides  were  first  applied  to  dormant  peach  trees.  So  far  as 
learned,  this  treatment  was  first  practiced  in  California,  being  intro- 
duced by  the  winter  application  of  sprays  for  the  destruction  of  the 
San  Jose  scale  {^AspldiotuH:  'pernlciosus).  This  insect  was  first  discov- 
ered in  the  Santa  Clara  Valle}^  about  18T0,  Init  some  time  had  elapsed 
between  the  date  of  its  introduction  and  the  use  of  the  stronger  winter 
sprays  for  its  control. 

Caustic  soda  and  potash  were  early  tested  against  this  insect,  and 
afterwards  sulphur  was  added,  the  sulphides  of  potassium  and  sodium 
being  used  by  many  growers.     Somewhat  later  whale  oil  soap  and  sul- 

'  Berlese,  A.  N.,  I  Parassiti  Yegetali  delle  Piante  Coltivate  o  Utili,  preface  dated 
1S94,  pp.  124-126. 

'■^Prillieux,  Ed.,  Mai.  d.  Plantes  Agr.,  Paris,  1895-97,  pp.  394-400. 

^  Weisz,  J.  E.,  Die  schiidlichsteii  Krankheiten  unserer  Feld-,  Obst-,  Gemuse-  und. 
Ciarten-Gewachse,  ]SIiinchen,  1898,  p.  45. 


HISTORY    OF   TREATMENT.  4'.) 

phur  were  eoinbineil  hy  l)oiliiio-.  and  still  hittT  a  fau>tic  >\)Vi\.y  contaiii- 
ino-  lime  was  tested.  AH  the  ahove  cheinicals.  cvfii  the  milk  of  !im<\ 
wore  applied  to  dormant  trees,  and  they  are  all  known  to  possess  sutK- 
cient  funoieidal  aetion  to  control  peaeh  leaf  curl  to  a  lar«i-o  extent  if 
applied  to  the  trees  shortly  befpre  they  bloom. 

While  many  growers  were  using  these  etiustie  and  sulphide  sprays, 
another  spray  eontaining  nuieh  larger  (juantities  of  sul})hur  was  being 
used,  and  proved  of  nuich  greater  power,  both  as  a  fungicide  and  insecti- 
cide. This  was  a  spray  containing  sulphur  and  lime,  or  a  sulphide  of 
calcium,  and  the  history  of  its  introduction  is  of  special  interest  and  is 
inseparable  from  the  early  hi.story  of  the  treatment  of  lurl.  Mr.  Alex- 
ander Craw,  quarantine  officer  of  the  California  State  Board  of  Horti- 
culture, has  published  an  account  of  the  introduction  of  this  spray  in  a 
recent  number  of  the  Pacific  Rural  Press,'  but  the  following  facts 
were  gleaned  froiu  those  who  were  the  tirst  to  use  and  introduce  the 
spraA'.'"  !Mr.  A.  T.  Covell,  who  tirst  applied  this  spray  to  dormant 
peach  trees,  near  Fresno,  Cal..  does  not  supph'  exact  dates  relative 
to  the  work,  but  Mr.  N.  W.  Motheral,  of  Hanford.  and  Mr.  I.  H. 
Thomas,  of  Visalia,  agree  in  placing  its  iirst  use  as  a  spray  in  the  year 
1880  or  1881.  The  writer  is  informed  by  Mr.  Motheral  that  the  lime, 
sulphur,  and  salt  solution  was  originally  used  as  a  sheep  dip  in  Aus- 
tralia, where  it  was  known  as  the  ''Victoria  lime-and-sulphur-dip"  for 
scab.  He  states  that  it  was  recommended  I)y  a  Dr.  Rowe,  and  offi- 
cially indorsed  for  a  sheep  dip  in  that  country.  This  dip.  it  is  also  said, 
was  introduced  in  California  by  Mr.  Charles  Hobler.  of  Hanford.  and 
Mr.  Hobler  claims  to  have  first  recommended  it  to  ^Mr.  Covell.  then 
living  near  Fresno,  for  the  treatment  of  his  infested  peach  trees.  Mr. 
Covell  disputes  this  claim,  but  holds  that  he  (Covell)  first  used  this 
solution  as  a  spray  upon  his  trees  with  success  in  the  control  of  the 
San  Jose  scale.  As  soon  as  this  spray  was  found  to  be  a  practical  suc- 
cess, ]Mr.  Covell,  ]Mr.  Thomas,  and  Mr.  Motheral  worked  for  its  gen- 
eral adoption  in  the  treatment  of  scale.  Mr.  Thomas  states  that  he 
sprayed  his  own  orchard  the  winter  after  seeing  the  action  of  the  spray 
on  Mr.  Covell's  trees,  and  about  this  time  the  facts  were  given  to  the 
press.  Mr.  Thomas  writes  that  thi.s  spraj'  was  in  general  use  in  and 
about  Visalia  as  earlv  as  1883,  1884,  and  1885,  and  in  Mr.  Motheral's 
.section,  near  Hanford,  at  the  same  time.  It  may  here  1)0  stated, 
however,  that  lime  and  sulphur  had  l)oen  united  by  boiling  in  water 
and  used  as  early  as  lS'y2,  at  least  in  hothouses,  for  controlling  the  dis- 
eases of  plants.  (See  Revue  Horticole,  1852,  p.  168,  and  Gardeners' 
Chronicle,  1852,  p.  419.) 

'Pacific  Rural  Press,  July  29,  1S99,  p.  6S. 

^Letters  from  I.  II.  Thomas,   Visalia,  Cal.,  Sept.  6,  18W;  X.   \V.  Motlieral,  Han- 
ford, Cal.,  Sept.  6,  1899;  and  A.  T.  Covell,  Woodbridge,  Cal.,  Oct.  \:i,  1899. 
19093— No.  20 4 


50     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

It  will  be  seen  hy  the  preceding  outline  that  jstrong  fungicidal  spraj^s 
were  in  general  winter  use  upon  peach  trees  throughout  much  of  Cali- 
fornia in  the  years  1880  to  1885,  during  which  time  the  peach  or- 
chards of  many  portions  of  the  State  were  Ijadly  affected  by  curl.  In  a 
report  by  Mr.  W.  G.  Klee.  who  inspected  the  orchards  in  man}-  counties 
of  California  from  July  to  September,  1886,  it  is  stated  that  in  Alameda 
County  the  cultivation  of  peaches  must  be  confined  to  such  varieties  as 
are  very  little  subject  to  leaf  curl ;  in  Santa  Cruz  County,  that ' '  peaches, 
of  course,  are  subject  to  curly  leaf,  and  can  not,  as  a  general  thing,  be 
considered  prolital)le;"  and  that  in  the  Santa  Rosa  Valley  the  peach  is 
"of  course  subject  to  curh"  leaf.''^ 

As  peach  leaf  curl  was  quite  prevalent  throughout  California  in 
1880-85,  and  as  a  large  number  of  peach  growers  treated  their  dor- 
mant trees  with  fungicidal  sprays  during  that  period,  it  is  not  strange 
that  they  soon  learned  that  the  winter  sprays  prevented  curl.  Mr.  I.  H. 
Thomas,  of  Visalia,  informed  the  writer^  that  it  was  about  the  year 
1885  that  he  noticed  that  the  orchards  sprayed  with  the  lime,  sulphur, 
and  salt  solution  were  entirely  free  from  leaf  curl,  while  orchards  con- 
tiguous were  affected  so  badly  that  all  the  foliage  fell  off". 

In  1886  Mr.  ^\.  G.  Klee  said.^  when  speaking  of  an  inspection  he 
made  of  the  orchard  of  Mr.  A.  Block,  of  Santa  Clara,  Cal. :  "A  treat- 
ment of  peaches  affected  with  curly  leaf  attracted  my  attention.  Trees 
not  subjected  to  this  treatment  were  in  verv  poor  condition,  while  the 
others,  favored  with  it,  were  in  fine,  healthy  bearing.'*  Mr.  Block  says 
respecting  this  work*  that  he  was  making  experiments  for  the  destruc- 
tion of  scale  insects  when  he  detected  a  perceptible  difference  in  the 
amount  of  curl  on  the  treated  and  the  untreated  trees.  He  thinks 
this  was  one  or  two  years  before  Mr.  Klee  had  seen  his  trees  in  1886. 
After  having  noticed  the  action  of  the  sprays  applied  for  scale  in  the 
prevention  of  curl,  he  went  to  work  to  ascertain  what  particular 
ingredient  caused  the  prevention  of  the  fungous  disease.  These  direct 
experiments,  Mr.  Block  states,  were  carried  out  on  a  row  of  23  trees 
in  his  orchard.  Among  the  chemicals  tested  were  caustic  soda,  caustic 
potash,  carbolic  acid,  tobacco,  and  sal  soda,  all  more  or  less  coml)ined 
with  whale  oil.  Among  the  numerous  sprays  used,  Mr.  Block  thinks 
that  a  strong  solution  of  caustic  soda  gave  the  best  results.  All  these 
sprays  were  applied  while  the  trees  were  dormant.^     The  stronger 

^Klee,  W.  G.,  Reports  and  Papers  Ijy  the  Inspector  of  Fruit  Pests,  read  at  Sacra- 
mento, November,  1886,  Kept.  Cal.  State  Bd.  Hort.,  1885-86,  pp.  344,  347,  349,  350. 

2  Letter  dated  Visalia,  Cal.,  Sept.  6,  1899. 

•^L.  c,  p.  347. 

*  Letters  dated  Santa  Clara,  Cal.,  Sept.  1  and  10,  1899. 

^  It  may  be  noted  that  whale  oil  soap  was  thus  used  by  Mr.  Block  with  success 
against  ciirl  in  1885  and  1886.  Prof.  L.  R.  Taft,  in  a  letter  dated  Agricultural  College, 
Mich.,  Aug.  31,  1899,  says  that  he  had  good  results  in  the  treatment  of  curl  with 
limewater,  lye,  and  whale  oil  soap.  (See  also  records  of  experiments  by  the  writer 
with  milk  of  lime,  etc.)     Mr.  F.  M.  Webster  reports  satisfactory  results  with  whale 


HISTORY    OF    TREATMENT.  51 

caustic  spra}'  recommended  by  Mr.  Block  consisted  of  I  pound  of  ;>8 
per  cent  caustic  soda  to  6  or  T  gallons  of  water.  The  same  year.  1n8(j, 
Mr.  Sol.  Runyon.  of  C'ourtland.  Cal.,  reported  that  he  had  met  with 
success  incontroUino-  a  ■"1)lii;ht"  of  peach  trees,  the  name  of  the  dis- 
ease not  ])eing  known  to  hini.  This  })light  had  })r('\iously  caused  all 
the  leaves  to  fall  from  every  tree  he  had.  especially  the  youiit--  ones. 
He  used  a  caustic  spray  on  the  dormant  tree,  as  did  Mr.  Block,  and 
states  that  the  trees  which  he  treated  were  not  atiected  by  th(>  blig-ht 
at  all.  while  the  untreated  trees,  right  l)eside  the  treated  ones,  were 
badly  atiected.^  There  is  little  dou))t  that  Mr.  Runyon  was  treating 
curl,  as  it  is  a  xevy  serious  trouble  in  that  section  of  the  State.  After 
the  leaves  had  fallen  in  the  autumn  of  1886  and  during-  the  winter  of 
1886-87,  ]Mr.  Runyon  sprayed  many  of  his  peach  trees  with  a  spra}' 
composed  of  2  gallons  fish  oil,  10  pounds  of  caustic  soda  (98  per  cent), 
and  5  pounds  of  copper  sulphate  to  100  gallons  of  water.  This  spray, 
as  applied,  was  certainly  a  preventive  of  curl,  and  as  a  portion  of  his 
peach  trees  were  left  untreated  the  contrast  should  have  been  marked. 
Unfortunately,  however,  1  have  been  unable  to  get  further  details  of 
this  early  work  with  copper  sulphate,  as  Mr.  Runyon  is  no  longer 
living.^ 

In  November,  1888,  Mr.  W.  G.  Klee  stated  at  the  Chico  meeting  of 
the  California  State  Board  of  Horticulture,  that  an  experienced  and  suc- 
cessful fruit  grower  in  San  Jose  had  used  successfully  for  the  purpose 
of  killing  scale  insects,  the  so-called  sal  soda  and  whale  oil  wash,  and 
that  he  maintained  that  ever  since  he  had  been  using  that  wash  he  had 
been  free  from  leaf  curl  in  his  orchard.^  Mr.  Joseph  Hale,  of  Stock- 
ton, Cal.,  reports  *  that  he  sprayed  his  peach  trees,  while  dormant,  in  the 
years  1888.  1889,  and  1890.  as  well  as  in  subsequent  years,  and  that  as 
a  result  he  sustained  no  loss  from  curl  during  these  j'ears.  He  used 
the  lime,  sulphur,  and  salt  spray.  ^Ir.  G.  W.  Ramsey,  of  Lotus, 
Cal.,  states  that  he  began  spraying  his  orchard  with  lime,  sulphur, 
and  salt  in  1890  or  possibh'  in  1891,  In  1895,  in  writing  of  his  past 
spray  work,  he  states  that  his  trees  had  not  been  affected  in  the  least 
bv  leaf  curl  since  he  had  ])een  using  the  above  wash.  He  says:  "It 
completely  exterminated  the  scale  the  first  two  years  I  used  it,  but  I 
continue  to  apply  it  to  my  trees  once  a  year  to  prevent  leaf  curl."  He 
further  states  that  this  wash  nuist  be  applied  when  the  ])uds  are  dor- 
mant, and  that  it  is  generally  applied  in  February  in  his  section. 

oil  soap  (South  AiL«tralian  J^nirnal  of  Agriculture,  Marcli,  1899,  Vol.  II,  No.  8,  p.  630) ; 
see  also  the  results  reported  by  Henry  Rofkar  and  W.  V.  Latham  &.  Son,  of  Catawba 
Island,  Ohio,  as  reported  by  A.  D.  Selby,  Bull.  No.  104,  pp.  208,  209.  Ohio  Agr.  Exp. 
Sta.,  March,  1899. 

'Rept.  Cal.  State  Bd.  Hort.,  188.3-86,  p.  221. 

-Il)id.,  1887-88,  p.  93. 

"Rept.  Cal.  State  Bd.  Hort.,  1889,  p.  172. 

*  Reply  to  circular  letter  of  Nov.  25,  1893. 


52     PEACH  LEAF  CURL!  ITS  MATURE  AND  TREATMENT. 

As  earl}'  as  1890  the  efl'ectiveness  of  lime,  sulphur,  and  salt  against 
curl  appears  to  have  been  observed  in  Oregon.  Mr.  J.  D.  Whitman, 
of  Medford,  Oreg.,  who  was  horticultural  commissioner  for  the  third 
district  of  that  State,  wrote  under  date  of  January  27,  1S!>4,  that  four 
3^ears'  observation  as  commissioner  had  demonstrated  beyond  a  doubt 
that  a  spray  of  lime,  .sulphur,  and  salt  is  an  effectual  remedy  for  leaf 
curl.  He  states  that  the  application  in  ever}^  instance  w^as  made  for 
the  purpo.se  of  destroying  the  San  Jose  or  pernicious  scale,  and  gener- 
alh'  on  only  a  portion  of  the  orchard,  the  other  portion  showing  the 
curl  as  usual. 

The  lirst  practical  experiments  with  copper  sprays  on  dormant  trees 
for  the  control  of  curl,  after  the  sprays  applied  by  Mr.  Sol.  Runyon 
in  1886  and  1887,  were  conducted,  so  far  as  learned,  in  the  3'ear  1890. 
The  siunmer  use  of  these  sprays  had  been  tested  in  Australia,  and 
proba))ly  elsewhere,  for  several  years,  but  with  slight  success  in  the 
control  of  curl. 

About  the  1st  of  Deceml^er,  1889,  Mr.  L.  E.  Benton,  then  of  Berke- 
ley, Cal.,  wrote  to  the  United  States  Department  of  Agriculture  for 
information  relative  to  the  nature  and  treatment  of  curl.  These  inqui- 
ries were  answered  at  length,  the  literature  on  Kroascus  deformans 
being  quite  fully  cited.  No  method  of  controlling  this  disease  was 
then  known  at  Washington,  and  as  winter  spra}" ing  had  not  yet  reached 
its  present  importance,  the  reco'mmendations  for  treatment  were  nec- 
essarily inadequate,  and  were  based  upon  the  then  accepted  views 
respecting  the  strict  perennial  nature  of  the  mycelium  of  the  fungus, 
and  the  consequent  difficult}'  of  controlling  the  parasite  by  sprays. 

After  gathering  such  information  as  he  desired,  Mr.  Benton  insti- 
tuted a  series  of  spraying  experiments  in  the  university  orchard  at 
Berkeley  in  the  spring  of  1890.  The  work  done  by  ]Mr.  Benton, 
although  limited  in  extent,  was  of  the  utmost  practical  importance,  as 
well  as  of  great  theoretical  interest.  A  summar}'  of  his  results  was 
published  in  August,  1890.^  Three  copper  ,spra^^s  were  tested,  the 
annnoniacal  copper  carbonate,  basic  copper  acetate  solution,  and  Bor- 
deaux mixture.  The  ammoniacal  copper  carbonate  was  applied  on 
February  28,  1890,  before  the  opening  of  the  buds.  All  three  of  the 
sprays  mentioned  were  also  tested  soon  after  the  leaves  started.  The 
results  demonstrated  that  winter  treatment  of  the  trees  with  the  salts 
of  copper  will  effectivel}'  control  the  disease,  but  that  summer  treat- 
ment Avill  not  control  it,  and  also  that  infection  of  the  spring  growth 
b}'  perennial  un^celium  was  the  exception  and  not  the  rule  with  this 
disease — facts  of  the  utmost  practical  importance  for  the  orchardist. 
Mr.  Benton's  studies  likewise  led  him  to  the  view  that  the  m^'celium, 
passing  from  infected  leaves  to  the  stem,  is  able  to  infect  new  foliage 

1  Pacific  Rural  Press,  Aug.  2,  1890. 


HISTORY    OF    TREATMENT.  58 

by  following-  close  ))ohind  the  growing  point  of  tho  stem.  His  o])serva- 
tions  seemed  to  point  to  this  young  niyoeliuni.  ivsulting  from  tlic  iirst 
spring  infections,  as  the  source  of  the  later  infections  through  the 
branches  rather  than  tiie  perennial  mycelium  of  the  previous  year. 
He  says  that  not  only  does  the  fungus  live  in  the  leaf  of  the  peach,  but 
it  at  once  pushes  its  way  into  the  young  growing  stem,  following  the 
growing  point  as  fast  as  it  lengthens  und  passing  into  the  leaves  as  fast 
as  they  appear.  On  this  account  he  concludes  that  no  external  appli- 
cations can  stop  such  a  fungous  growth,  and  spraying  after  the  buds 
burst  and  the  fungus  has  become  estal)lished  will  have  little  effect.  It 
ma}'  be  added  that  several  3'ears'  ol)servation  in  large  Ijlocks  of  trees 
sprayed  after  the  foliage  had  started  lias  shown  the  writer  that  the  dis- 
ease can  not  thus  l)e  controlled,  and  that  ]Mr.  Benton's  conclusions  are 
correct.  Whether  this  failure  is  due  to  the  causes  pointed  out  by  ]\Ir. 
Benton,  however,  or  simply  to  the  lack  of  the  prevention  of  the  infec- 
tion by  spores,  or  to  both  sources  of  infection,  should  be  giA'en  further 
study.  Mr.  Benton  states  that  in  the  spring  of  1890.  the  time  his 
experiments  were  undertaken,  '"no  remedy  was  known;  since,  some 
practical  growers  have  found  successful  means  of  comliating  it.  and 
these  experiments  now  deserve  no  further  credit  than  that  they  were 
intentional  and  not  a  matter  of  chance."  It  is  now  known  that  curl 
had  been  controlled  l)y  numerous  growers  in  widely  separated  regions 
in  California  through  the  use  of  various  sprays  many  years  prior  to 
1890.  Mr.  Benton  says  he  was  unaware  of  tliese  facts  when  he  began 
his  work,  and  his  experiments  are  worthy  of  full  credit,  not  alone  for 
the  enterprise  shown  in  undertaking  them.  ])ut  for  the  results  of 
unquestioned  A'alue  to  which  they  led. 

In  1891  the  copper  treatment  for  peach  leaf  curl  was  independently 
discovered  and  clearly  demonstrated  in  Australia.  The  successful 
results  of  this  work  were  observed  in  November  and  Deceml)er.  1891, 
and  were  published  in  the  South  Australian  Register  of  March  80. 189*2. 
At  a  meeting  of  the  Nuriootpa  branch  of  the  South  Australian  Agri- 
cultural Bureau,  held  in  Angaston  during  November.  1890,  the  sub- 
ject of  fungous  diseases  atiecting  fruit  trees  was  discussed  and  the 
appointment  of  a  committee  to  conduct  preventive  experiments  was 
considered.  At  a  subsequent  meeting  Messrs.  F.  C.  Smith.  W.  Sage, 
and  A.  B.  Robin  were  selected  for  this  work.  During  the  interval 
before  spraying,  Mr.  Smith  corresponded  with  those  in  charge  of  the 
pathological  departments  in  Australia.  England.  California,  and  Wash- 
ington. The  report  in  the  South  Australian  Register  says  that  among 
the  replies  received  was  a  series  of  valuable  reports  from  Professor 
Galloway,  showing  that  up  to  1889  modified  can  celeste,  annnoniacal 
copper  carbonate,  and  Bordeaux  mixture  had  proved  most  successful 
in  the  United  States.  "These  were  therefore  selected  by  the  commit- 
tee for  their  experiments."    Mr.  Smith,  of  this  committee,  informed 


54     PEACH  LEAF  CURL!  ITS  NATURE  AND  TREATMENT. 

the  writer  that  their  work  was  based  largely  upon  that  of  Prof.  E.  S. 
Goff  on  Fusicladium.^ 

The  spray  work  was  begun  in  July,  before  the  trees  leafed  out,  the 
main  object  being  to  control  apple  scab  and  the  shot-hole  fungus  on 
the  apricot.  The  sprayed  apricot  trees  belonged  to  Mr.  Trescowthick, 
and  were  treated  with  Bordeaux  mixture.  In  the  block  was  one 
peach  tree,  which  was  sprayed  when  the  apricots  were  treated.  This 
tree  had  suffered  severel}^  from  curl,  so  much  so,  in  fact,  that  it  had 
not  borne  for  four  or  five  years,  but  after  spraying  it  yielded  eight 
cases  of  fruit  of  50  pounds  each,  or  -iOO  pounds,  the  curl  being  almost 
entirely  prevented.  Mr.  Smith  writes,  respecting  this  work,  that 
when  apph'ing  Bordeaux  mixture  from  July  to  October,  1891,  for  the 
various  diseases  with  which  they  w^ere  coping  he  had  not  the  slightest 
idea  that  this  or  any  of  the  fungicides  would  have  anj^  effect  whatever 
on  curl  leaf,  and  the  members  of  the  committee  were  the  more  sur- 
prised to  see  its  marvelous  effects  in  January  and  February.  ' '  It  was 
the  most  conclusive  of  all  our  tests,"  it  was  stated." 

The  work  was  continued  the  following  season,  and  some  contrasts 
obtained  on  the  place  of  Messrs.  Sidney  Smith  &  Son,  of  Yalumba,  are 
of  interest  in  this  connection.  In  an  article  published  at  that  time  it 
is  stated  that  the  effects  of  spraying  with  Bordeaux  mixture  upon  both 
peaches  and  apricots  were  very  noticeable.  On  one  side  of  the  fence 
was  seen  a  healthy  set  of  trees,  well  clothed  with  fruit  and  dark  green 
foliage,  and  with  no  curled  leaves,  while  on  the  other  side,  where  spra}'- 
ing  had  not  been  done,  was  a  block  of  apricots,  among  which  were  a 
few  peach  trees  very  badl}'^  attacked  by  leaf  curl.  At  this  time  the 
orchard  of  Mr.  A.  B.  Robin,  of  Nuriootpa,  secretar}^  of  the  committee 
for  experiments,  was  inspected  b}^  Mr.  Molineaux,  general  secretary 
of  the  South  Australia  Agricultural  Bureau,  and  by  several  prominent 
horticulturists,  and  was  found  to  have  a  splendid  crop  of  fruit,  nearly  all 
the  apricot  and  peach  trees  having  been  sprayed.  One  peach  tree  had 
been  sprayed  on  only  one  side  with  the  Bordeaux  mixture,  and  on  this 
side  the  foliage  was  clean  and  health}^,  while  on  the  unsprayed  side  it 
was  curled.  "Here  again,"  says  the  reporter  of  this  examination, 
"was  absolutely  conclusive  evidence  of  the  preventive  effect  of  spray- 
ing for  curl  leaf." 

In  the  United  States,  in  1892,  the  use  of  both  the  sulphur  and  copper 
sprays  on  dormant  trees  was  much  more  common.  The  control  of 
curl  was  a  new  discovery  to  several  growers  who  had  not  heard  of 
the  published  experiments.  Mr.  George  Woolsey,  of  lone,  Cal.,  had 
been  considerably  troubled  by  a  shot-hole  fungus  affecting  peach  twigs — 
a  conunon  trouble  in  the  northern  portion  of  the  State.  A  bundle  of 
the  affected  twigs  was  sent  to  Professor  Woodworth,  of  Berkelev,  who 

'Letter  dated  Angaston,  South  Australia,  Feb.  11,  1895. 
^Letter  dated  Angaston,  South  Australia,  Apr.  6,  1895. 


HISTORY    OF    TREATMENT.  55 

advised  the  use  of  Bordeaux  mixture;  but  us  this  fungus  i.s  active  in 
the  spring  before  the  trees  leaf  out,  Mr.  Woolsey  spraj'ed  the  trees  while 
dormant.  He  says,  in  relation  to  his  results,  that  ho  found  Bordeaux 
mixture  corrected  the  trouble  with  the  twigs,  and  at  the  same  time  acted 
as  a  specific  for  the  leaf  curl.  ^  His  work  for  the  control  of  curl  in  the 
following  year  was  strikingly  conclusive  as  to  the  effectiveness  of  this 
spray.  Mr.  D.  W.  Sj'lvester,  of  Gej'serville,  Cal.,  conducted  some 
spraying  experiments  in  1892  with  the  direct  object  of  controlling  curl. 
His  spray  was  composed  of  12  pounds  of  copper  sulphate  and  20  pounds 
of  lime  to  100  gallons  of  water,  and  was  applied  to  the  dormant  trees. 
Mr.  Sylvester  states  that  having  formed  the  opinion  that  the  disease 
was  of  fungous  nature,  and  knowing  of  the  value  of  copper  sulphate  as 
a  fungicide,  he  determined  to  test  it  against  curl.  He  believed  better 
results  would  be  obtained  by  killing  the  "germ"  than  by  waiting  until 
the  disease  appeared,  and  this,  he  says,  induced  him  to  make  the  appli- 
cation to  the  dormant  trees.  For  the  experiment  he  selected  a  row  of 
10  trees,  spraying  5  and  leaving  5  unspraved  for  comparison.  He 
states  that  the  5  sprayed  trees  held  their  leaves  and  fruit  and  bore  a 
crop,  but  the  others  shed  every  leaf  and  every  peach,  and  for  more 
than  a  month  looked  as  if  a  fire  had  gone  over  them.  In  spite  of  this 
experience,  Mr.  Sylvester  neglected  to  spra}'  in  1S03,  when,  he  states, 
the  trees  shed  all  their  leaves  and  nearly  all  their  fruit  through  curl,  ^ 
and  adds  that  the  best  time  to  spray  is  just  as  the  buds  begin  to  swell. 
A  portion  of  the  peach  trees  on  the  Rio  Bonito  ranch  at  Biggs,  Cal., 
were  sprayed  with  the  lime,  sulphur,  and  salt  spray  in  1892,  the  spray 
being  applied  to  the  dormant  trees  as  elsewhere.  The  contrast  that 
season  between  the  sprayed  and  unsprayed  trees  was  well  marked,  the 
unspraj'ed  trees  l)eing  much  affected  by  curl,  while  those  treated  were 
practically  free  from  it.  These  observations  were  made  at  the  time 
by  Mr.  McDonald,  the  foreman,  and  by  others  on  the  ranch. 

The  preceding  examples  could  be  greatly  extended  if  necessary,  as 
winter  spraying  was  a  common  practice  in  California  after  1885.  By 
1892  the  San  Jose  scale  had  also  become  more  widely  distributed  in 
Oregon,  and  was  being  quite  general!}'  treated  by  ^vinter  sprays  in  that 
State.  Mr.  A.  H.  Carson,  of  Grants  Pass,  Oreg. ,  began  spraj'ing  his 
orchard  about  this  time.  In  reply  to  a  communication  sent  to  him 
November  25, 1893,  Mr.  Carson  saj's  that  his  knowledge  as  to  the  lime, 
sulphur,  and  salt  remedy  for  leaf  curl  was  gained  by  observing  that 
trees  on  which  this  remed}-  was  used  to  destroy  the  San  Jose  scale  were 
not  affected  by  curl,  although  they  were  varieties  much  subject  to  the 
disease.  On  the  other  hand,  he  states  that  unsprayed  trees,  with  the 
same  conditions  as  to  exposure,  altitude,  etc.,  were  badly  affected. 
Mr.  J.  H.  Stewart,  of  Medford,  Oreg. ,  writes  that  he  spra^'ed  his  peach 

^  Letter  dated  lone,  Cal.,  Aug.  26,  1899. 

2 Letters  dated  Geyserville,  Cal.,  Nov.,  1893,  and  Sept.  18,  1899. 


56     PEACH  LEAF  CUKLI  ITS  NATURE  AND  TREATMENT. 

trees  in  1892.  ^  He  saj's  he  used  a  spray  in  1892,  1893,  and  1894, 
which  was  effectual  against  scale  and  most  fungi.  This  spra}"  was 
composed  of  lime,  sulphur,  and  sulphate  of  copper,  and  was  applied 
in  the  winter. 

In  the  East,  about  this  time,  mildew,  brown  rot,  black  spot,  rust,  and 
curl  were  attracting  the  attention  of  peach  growers  and  causing 
serious  losses  in  some  sections,  and  a  good  many  growers  were  trying- 
summer  sprays  for  the  control  of  one  or  more  of  them.  Mr.  F.  P. 
Herr,  of  Ridgely,  i\Id.,  writes^  that  for  three  successive  years  prior 
to  1895  he  sprayed  with  limewater,  Bordeaux  mixture,  and  arsenical 
mixtures,  and  that  everything  he  used  produced  aljsolutely  negative 
results,  except  the  arsenites,  which  injured  both  foliage  and  fruit.  It 
would  appear  probable  from  these  results  that  the  sprays  were  applied 
too  late  to  be  effective  against  curl.  Mr.  L.  B.  Geiger,  of  Hoffman, 
Pa.,  writes^  that  he  was  formerly  troubled  with  leaf  curl  in  his 
orchard,  but  has  had  verj^  little  of  late  years.  The  reason  of  this,  he 
thinks,  is  the  fact  that  he  has  sprayed  his  peach  trees  with  Bor- 
deaux mixture  several  times  each  3^ear  since  1892.  He  states  that  at 
least  To  per  cent  of  the  crop  of  one  variety  was  thus  saved.  Whether 
the  spray  work  was  done  in  the  winter,  or  whether,  owing  to  the 
number  of  applications  made,  the  summer  spray  persisted  in  its  action 
through  the  following  winter,  is  not  known. 

It  was  in  1892  that  Prof.  L.  R.  Taft,  of  the  ^Michigan  Agricultural 
Experiment  Station,  first  obtained  the  idea  that  peach  leaf  curl  could 
be  controlled  l)y  the  application  of  winter  sprays.  This  gentleman 
has  supplied  the  leading  facts  respecting  his  work.*  He  says:  "In 
1892  I  was  making  a  series  of  experiments  with  Bordeaux  mixture 
and  solutions  of  copper  sulphate  to  learn  the  strength  that  could  be 
used  upon  various  plants  and  trees  without  injury.  These  materials 
were  applied  at  different  times,  the  sprayings  being  at  intervals  of 
about  four  weeks,  from  April  to  July,  and  while  some  trees  received 
but  one  application,  others  were  sprayed  two,  three,  and  four  times. 
It  was  noticed,  the  trees  sprayed  in  April  with  either  copper  sulphate 
or  Bordeaux  mixture  had  no  curled  leaves,  while  unspra^'ed  trees  and 
those  that  were  not  sprayed  until  June  or  July  were  seriousl}'  injured 
by  leaf  curl. 

"From  the  marked  difference  in  the  injury  from  the  leaf  curl  to 
the  spra3'ed  and  unsprayed  trees,  I  felt  ver}-  confident  that  the  disease 
could  be  held  in  check  to  a  large  extent  b}^  the  use  of  fungicides,  and 
in  writing  Bulletin  92,  in  December,  1892  (published  in  March,  1893), 
I  make  the  statement  that  '  it  is  quite  certain  that  the  disease  can  be, 
to  some  extent,  held  in  check  bj'  their  use,'  in  referring  to  the  effect 

1  Letters  dated  Medford,  Oreg.,  Dec.  14,  1894. 

''Letter  dated  Ridgely,  Md.,  Feb.  15,  1895. 

^Letter  dated  Hoffman,  Pa.,  Mar.  18,  1895. 

^Letter  dated  Agricultural  College,  Mich.,  Aug.  31,  1899. 


HISTORY    OF    TREATMENT.  57 

of  fungicides  in  preventing-  the  development  of  leaf  curl  on  peach 
trees." 

It  would  seem  that  the  work  in  Australia,  as  well  as  that  of  the  pre- 
ceding ten  3'ears  in  California,  had  not  come  under  the  notice  of  Pro- 
fessor Taft  at  the  time  of  his  observations  in  1892.  and  that  the  same 
was  true  at  the  close  of  the  succeeding  year's  experiuK^nts.  In  his 
article  on  curl,  published  in  the  American  Agriculturist  for  February, 
1894,  he  says,^  in  speaking  of  the  treatment  of  curl  prior  to  his 
work  in  1893:  ''Although  there  were  some  vague  suggestions  as  to 
the  possible  value  of  some  of  the  fungicides  as  remedies  for  this  dis- 
ease, nothing  was  reallv  knoAvn  until  the  past  season."" 

jNIay  20,  181»3,  while  working  on  plant  diseases  at  Yul)a  City,  Cal., 
in  company  with  Mr.  R,  C.  Kells.  then  horticultural  commissioner  of 
Sutter  County,  that  gentleman  told  the  writer  of  a  peach  orchard  in 
the  vicinity  where  peach  leaf  curl  had  been  controlled  hy  the  previous 
winter's  sprays.  The  orchard  was  that  of  Mr.  W.  H.  Campbell,  of 
Yuba  City,  and  was  at  once  examined  by  the  writer  in  company  with 
Mr.  Kells.  The  trees  were  of  the  Orange  Cling  variety,  and  had  l)een 
sprayed  with  lime,  sulphur,  and  salt  up  to  the  base  of  the  smaller 
liranches  of  the  main  limbs,  for  the  purpose  of  killing  the  San  Jose 
scale  upon  the  older  wood,  the  spraying  of  the  tops  of  the  trees  not 
being  necessary.  The  result  of  this  treatment  was  to  protect  the 
lower  half  of  the  trees  from  the  attack  of  curl,  while  the  tops  were 
left  unprotected.  Curl  developed  seriously  in  the  Sacramento  Valley 
that  spring,  and  as  a  consequence  these  trees  were  badly  diseased  and 
stripped  of  foliage  down  to  the  line  where  the  limbs  had  been  sprayed 
for  San  Jose  scale.  The  resulting  appearance  was  most  striking,  and 
showed  the  advantages  of  spraying  in  a  marked  degree.  The  lower 
half  of  the  trees  was  well  supplied  with  normal  green  foliage,  while 
the  upper  half  was  either  bare  or  the  leaves  present  were  yellow  and 
Ijadl}'  curled.     Photographs  of  these  trees  were  taken  on  May  21. 1893. 

Ma}'  22,  1898.  the  writer  visited  the  Riviera  orchard,  at  Live  Oak, 
Cal.  This  orchard  is  situated  on  the  Feather  River  bottom  and  is 
under  the  management  of  Mr.  A.  D.  Cutts,  of  Live  Oak,  one  of  the 
proprietors.  In  this  orchard  was  found  a  most  striking  case  of  the  pre- 
vention of  cull  by  the  use  of  winter  sprays.  In  the  winter  of  1892-93 
one  block  of  trees  was  thoroughly' sprayed  for  San  Jose  scale  with  lime, 
sulphur,  and  salt.  After  this  work  was  completed  the  weather  became 
unfavorable  for  further  spraying.  The  soil  was  so  wet  from  rains  that 
a  40-acre  block  of  Crawf  ords  Late  trees  could  not  l)e  sprayed,  and  it  was 
so  late  in  the  winter  before  the  work  could  be  done  that  Mr.  Cutts 
feared  it  might  injure  the  fruit  buds  if  he  sprayed  the  trees  entire. 
He  therefore  had  the  trees  in  this  block  examined,  and  rags  were 
tied  upon  the  limbs  of  those  which  appeared  to  most  need  a  thorough 

^The  Curl  of  the  Peach,  American  Agriculturist,  Feb.,  1894,  pp.  71,  72. 


58  PEACH    LEAF    CURL*.    ITS    NATUEE    AND    TREATMENT. 

spraying  for  scale.  These  marked  trees  were  scattered,  here  and  there 
one,  throughout  the  entire  40-aere  block.  In  February  the  marked 
trees  were  very  thoroughly  sprayed  over  all  parts,  as  much  as  two 
gallons  of  spray  being  applied  to  each  tree.  After  this  work  was 
completed  the  entire  block,  with  the  exception  of  the  trees  already 
treated,  was  sprayed  as  high  as  the  forks  of  the  main  limbs,  thus 
avoiding  any  injury  to  swelling  buds.  As  before  stated,  curl  devel- 
oped seriously  in  the  Sacramento  Valley  in  the  spring  of  1893,  and 
the  result  was  that  the  unsprayed  trees,  as  well  as  those  sprayed 
only  on  the  main  limbs,  ^ere  nearly  denuded  by  the  disease,  while 
the  scattered  trees  which  had  been  spraj^ed  throughout  were  in 
full  and  vigorous  foliage  and  growth.  In  the  writer's  notes  upon  the 
examination  of  this  orchard  on  May  22,  1893,  it  is  stated  that  the 
trees  fully  treated  in  this  block  were  loaded  with  fruit  and  in  full  leaf, 
while  the  trees  sprayed  only  to  the  forks  of  the  limbs  were  nearly  bare 
and  almost  wholly  destitute  of  fruit  on  the  unsprayed  parts.  Such 
fruit  as  was  found  on  the  unspraj^ed  branches  was  inferior  in  size  and 
quality.  It  is  further  stated  that  the  absence  of  fruit  on  the  untreated 
branches  as  compared  with  the  abundant  yield  of  the  treated  branches 
gives  such  a  striking  contrast  as  to  be  almost  beyond  belief.  ^ 

Mr.  William  N.  Runyon,  of  Courtland,  Cal.,  treated  a  large  acreage  of 
peach  trees  with  lime,  sulphur,  and  salt  in  the  winter  of  1892-93.  He 
states  that  the  trees  sprayed  once  while  dormant  were  practically  free 
from  curl,  while  trees  of  the  same  variety  not  sprayed  were  badly 
affected.^  He  also  gives  an  observation  of  interest  in  connection 
with  the  habits  of  the  fungus,  and  one  since  indorsed  by  the  writer, 
that  is,  that  the  disease  ""will  not  spread  from  an  unsprayed  to  a  sprayed 
tree."  In  letters  from  Mr.  Runyon^  relative  to  this  work,  he 
remarks  that  although  he  had  heard  that  a  mixture  of  lime,  sulphur, 
and  salt  was  benelicial  in  controlling  curl,  he  had  no  idea  that  the  result 
would  be  so  nearly  a  complete  prevention.  He  says  that  it  was  only 
when  curl  leaf  had  become  quite  prevalent  on  unsprayed  trees  that 
he  noticed  its  almost  total  absence  on  those  that  had  been  spraj^ed. 
The  most  striking  instance,  he  states,  was  where  about  50  three  j-ear 
old  nectarine  trees  stood  in  rows  adjoining  about  a  dozen  full-grown 
trees  of  the  same  variety  that  had  shown  curl  for  years.  The  young 
trees,  not  having  shown  any  scale,  were  left  unsprayed,  and  were  a 
mass  of  curl,  while  the  old  trees,  which  were  given  the  regular  treat- 
ment, were  almost  entirel}'  free.  In  this  orchard  about  60  acres  of 
peach  trees  were  also  sprayed,  the  work  being  done  about  the  1st  of 

^  For  further  notes  and  tabulated  records  of  some  of  this  work  of  the  spring  of 
1893  the  reader  is  referred  to  Chapter  VII  under  Notes  on  the  Auxiliary  Experi- 
ments in  California. 

^  Answer  to  circular  letter  of  Nov.  25,  1893. 

3  Letters  dated  Courtland,  Cal.,  Jan.  31,  and  Mar.  8,  1894. 


HISTORY    OF    TREATMENT.  59 

February,  aud  40  acres  of  young  trees  left  unsprayed.  In  the  Santa 
Clara  Valley  the  sulphur  sprays  were  in  general  use  by  the  leading 
growers  in  1893.  Mr.  A.  B.  Elder,  of  Santa  Clara,  writes,  in  reply 
to  a  circular  letter  of  November  25  of  that  year,  that  this  spray  is 
giving  good  satisfaction  for  the  control  of  curl  and  "is  used  by  large 
growers  of  peaches."  Mr.  John  Rock,  of  Niles,  Alameda  County, 
Cal.,  writes,  under  date  of  December  28,  1893,  that  a  mixture  of  lime, 
sulphur,  and  salt  is  a  preventive  of  curl  if  applied  before  the  flower 
buds  expand. 

Bordeaux  mixture  was  used  in  the  winter  of  1892-93,  in  the  Carmel 
Valley,  near  Old  Monterey,  with  the  express  purpose  of  controlling 
curl,  Mr.  Daniel  Snively,  of  Gubserville,  Cal..  writes^  that  his 
brother  used  Bordeaux  mixture  for  the  control  of  this  disease,  and 
that  its  action  is  "  so  certain  that  any  twig  not  touched  is  sure  to 
curl."'  Mr,  George  Woolsey,  of  lone,  Amador  County,  Cal.,  sprayed 
his  orchard  with  Bordeaux  mixture  in  the  winter  of  1892-93,  for  the 
express  purpose  of  controlling  curl,  and  as  a  result  of  his  experiments 
in  the  winter  of  1891-92,  to  which  reference  has  already  been  made. 
Relative  to  his  work  in  the  spring  of  1893,  ]Mr.  Woolsey  says^  that  he 
sprayed  all  of  his  apricot  trees,  but  as  time  pressed  he  found  that  he 
would  not  be  able  to  spray  all  of  his  peach  trees,  so  ho  sprayed  the 
most  valuable  portion,  i.  e.,  the  young  lower  growth,  and  left  the  top 
unsprayed.  He  states  that  the  season  of  1893  was  damp,  and  leaf  curl 
very  prevalent  in  his  neighbors''  orchards,  but  on  his  place  all  the 
trees  and  parts  of  trees  sprayed  w^re  exempt,  all  the  others  being 
badly  affected  by  curl  and  the  crop  on  them  almost  a  failure.  A 
healthy  growth  on  the  lower  sprayed  part  of  the  trees,  and  the  branches 
denuded  of  foliage  on  the  upper  unsprayed  part,  formed  "a  most 
striking  object  lesson,"'  and,  Mr.  Woolsey  adds,  has  made  him  "an 
enthusiast  on  Bordeaux  mixture.''  A  few  demonstrations  such  as 
he  obtained  in  the  season  of  1893,  he  remarks,  would  convince  the 
growers  of  the  profitableness  of  the  work. 

^Nlany  peach  orchards  were  sprayed  in  Oregon  in  the  winter  of 
1892-93.  A  favorite  spray  was  a  combination  of  the  sulphur  spray 
with  copper  sulphate,  although  the  former  was  used  separately  by 
some  growers.  The  object  of  the  combined  spray  was  to  unite,  as  far 
as  possible,  the  insecticidal  qualities  of  the  sulphur  spray  with  the 
fungicidal  qualities  of  the  copper  salts.''  The  winter  application  of 
aumioniacal  copper  carbonate  was  tested  in  Oregon  also,  by  ]\Ir.  M.  O. 
Lownsdale,  of  Lafayette.  In  repl}^  to  the  circular  letter  dated  Nov- 
ember 25,  1893,  Mr.  Lownsdale  says  he  had  fair  success  in  prevent- 
ing curl  with  lime,  sulphur,  and  salt  applied  in  the  winter,  followed 

'  Reply  to  circular  letter  of  Nov.  25,  1893. 
2 Letter  dated  lone,  Cal.,  Mar.  26,  1894. 
• '  See  results  of  the  tests  of  combined  sprays  made  liy  the  writer,  pp.  84, 86, 117,  liS. 


60     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

by  three  applications  of  ammoniacal  copper  carbonate  after  the  appear- 
ance of  the  foliage.  He  had  better  success,  however,  from  ammoniacal 
copper  carbonate  applied  in  late  winter,  before  the  swelling  of  the 
buds,  followed  by  three  applications  of  a  weaker  solution  upon  the 
foliage.     "This.''  he  says,  "was  a  complete  success." 

In  Michigan  the  work  in  1893  was  very  satisfactory.  ]Mr.  Charles 
Youngreen,  of  Whitehall,  sprayed  one  row  of  peach  trees  before  the}' 
leafed  out  in  the  spring.  He  states  ^  that  not  one  of  the  sprayed  trees 
showed  curl,  while  the  unsprayed  trees  were  all  affected.  The  follow- 
ing year  he  sprayed  the  entire  orchard  and  not  a  tree  suffered  from 
the  disease.  At  Shelby.  Oceana  County,  several  growers  sprayed 
with  Bordeaux  mixture  with  good  success.  Mr.  K.  Morrill,  of  Benton 
Harbor,  stated  at  a  meeting  of  the  Michigan  Horticultural  Society 
held  at  Shelby.  June  14  and  15.  1893.  that  he  found  there,  in  four  or  five 
cases,  that  men  had  sprayed  peach  trees  with  Bordeaux  mixture,  and 
the  effect  in  decrease  of  leaf  curl  was  plain  to  be  seen."  jNIr.  Morrill 
fails  to  state,  however,  whether  the  lirst  spraying  was  done  while  the 
trees  were  dormant.  The  effects  of  curl  at  Shelby  at  that  time  were 
marked,  the  same  gentleman  remarking  that  in  one  morning  he  had  seen 
enough  damage  done  by  it  to  pay  for  spraying  all  the  orchards  within 
five  miles. 

Professor  Taft  reports  his  work  in  1893  as  follows:^  "In  order  to 
secure  definite  knowledge  upon  the  subject  [treatment  of  curl],  I 
arranged  for  a  series  of  experiments,  and  in  the  fall  of  1892  had  a 
number  of  peach  trees  sprayed  with  a  solution  of  copper  sulphate 
(1  pound  in  25  gallons),  and  in  a  similar  experiment  at  South  Haven 
Bordeaux  mixture  was  used  as  soon  as  the  leaves  dropped  in  Novem- 
ber, 1892.  During  the  tirst  half  of  April,  1893.  the  same  trees  were 
again  sprayed  with  similar  mixtures,  and  other  trees  were  treated  that 
had  not  been  sprayed  in  the  fall  of  1892.  The  result  was  that  where 
fully  50  per  cent  of  the  leaves  and  all  of  the  fruit  di'opped  from  the 
unsprayed  trees,  there  was  little  injurv  to  the  same  varieties  that  were 
treated  in  both  fall  and  spring  or  that  were  sprayed  only  once,  in 
April;  but  where  the}'  were  not  sprayed  until  after  the  leaves  had 
come  out  only  a  slight  benefit  was  secured.  The  results  were  given 
in  Bulletins  103  and  104  of  the  Station.  On  June  14,  1893.  I  gave  the 
results,  up  to  that  time,  at  the  meeting  of  the  State  Horticultural 
Societj'. '' 

The  orchards  of  the  Michigan  Agricultural  Experiment  Station  at 
South  Haven,  in  charge  of  JNIr.  T.  T.  Lyon,  had  suffered  severely  from 
curl  in  1890,  1891,  and  1892.*     Mr.  Lyon  says,  respecting  the  spraj'^ 

1  Letter  dated  Whitehall,  Mich.,  Sept.  6,  1899. 

=^  Kept.  Mich.  State  Hort.  Soc,  1893,  p.  68. 

*  Letter  dated  Agricultural  College,  Mich.,  Aug.  30,  1899. 

*See  Repts.  Mich.  Hort.  Soc,  1890,  p.  144;  1891,  p.  228;  1892,  pp.  160,  161. 


HISTORY    OF    TREATMENT.  61 

work  done  in  the  winter  of  1892-93,^  that  as  the  apparent  result  of 
the  fall  and  spring-  sprayings,  there  was;  almost  a  total  absence  of  leaf 
curl,  although  it  had  usuall\^  been  quite  prevalent  there  in  early  spring, 
and  was  present  in  1893  in  neighboring  orchards,  causing  many  of  the 
leaves  and  fruits  to  drop.  He  says'"  further,  that  to  him  "the  effect 
of  the  spra}"  upon  leaf  curl  in  particular  was  a  revelation."  The  work 
of  Professor  Taft  in  this  orchard  in  1893  was  reported  on  several  occa- 
sions during  1893  and  1894.^ 

The  work  of  the  writer  began  in  Michigan  by  the  publication,  in 
the  fruit  belt  of  that  State,  in  the  latter  part  of  July.  1893,  of  notices 
of  the  work  done  in  California.*  and  of  requests  for  the  names  of 
peach  growers  who  had  sustained  losses  from  this  disease.  In 
August,  plans  for  experiments  at  Shelby  and  Ludington  were  in 
progress,  and  in  November  a  circular  letter,  stating  that  leaf  curl  had 
been  successfully  prevented  in  California,  was  addressed  to  the  peach 
growers  of  all  the  leading  peach  centers  of  the  country.  In  this 
circular  it  was  stated  that  "It  is  proposed  to  carry  on  during  the 
coming  season  some  work  in  different  parts  of  the  United  States." 
The  circular  reached  many  of  the  leading  peach  growers  of  Michi- 
gan. During  the  winter,  that  of  1893-94,  plans  for  the  testing  of 
winter  sprays  for  the  control  of  curl  were  undertaken  by  growers,  at 
the  request  of  this  Department,  at  Whitehall.  Albion.  Ganges.  Beulah, 
Riverside,  Benton  Harbor,  St.  Joseph,  Kalamazoo,  Covert.  Hawk- 
head,  South  Haven,  Ludington,  Shelby,  Douglas,  Millgrove.  Custer, 
Amber,  Mears,  Hart,  Gobleville.  Ortonville,  Monterey.  Fenville, 
Saugatuck,  Allegan,  Wayland,  Bradley,  Peach  Belt,  etc.  During  the 
winter  of  189-1-95  the  above  list  was  greatly  extended.  Within  these 
two  3'ears  over  400  ^lichigan  peach  growers  were  sent  full  instruc- 
tions for  controlling  curl.  Each  grower  was  requested  to  make  his 
tests  according  to  an  experiment  sheet  sent  him,  leaving  unsprayed 
trees  for  comparison.  In  this  way  man}-  striking  object  lessons  were 
obtained,  aiding  materially  in  the  early  and  widespread  introduction 
of  the  methods  of  treatment  recommended.  Reports  of  a  few  of  these 
experiments  are  given  in  a  subsequent  chapter. 

The  Department's  tests  in  Ohio  were  instituted  through  a  circular 
letter  in  November,  1893,  announcing  to  a  large  number  of  peach 
growers  in  that  State  the  successful  treatment  of  curl  in  California, 
and  stating  that  experiments  would  be  undertaken  in  the  East.  As  a 
result  of  replies  to  this  circular,  full  instructions  for  controlling  curl 

iMich.  Exp.  Sta.  Bull.  Xo.  104,  pub.  Feb.,  1894,  pp.  64,  65. 

^  Letter  dateil  South  Haven,  Mich.,  Dec.  16,  1897. 

^  Paper  read  at  Shelby,  June  14,  1893,  Kept.  Mich.  Hort.  Soc,  189:1,  pj..  66,  67,  and 
79;  article  in  Allegan  Gazette,  July  1,  1893;  Mich.  Exp.  Sta.  Bull.  No.  Hi4.  p.  64;  pul). 
Feb.,  1894;  American  Agriculturist,  Feb.,  1894,  pp.  71,  72. 

*  Ludington  (Mich.)  Appeal,  issue  of  July  20,  1S93,  quoted  by  Shelby  Sentinel,  etc. 


62     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

■were  sent  to  a  number  of  orchardists  in  the  peach-growing  centers 
of  Ohio  in  the  winter  of  1893-94.  During  this  and  the  succeedino- 
winter  over  tiftj  orchardists,  located  in  twentj'-five  different  peach- 
growing  centers  of  the  State,  received  carefully  prepared  instructions 
for  winter  spraying  for  curl.  The  instructions  for  both  winters  were 
planned  in  the  usual  manner  of  experimental  work,  a  number  of 
unsprayed  or  control  trees  being  left  for  comparison  with  the  trees  to 
be  treated  with  each  spray  to  be  tested.  The  ol>ject  in  thus  planning 
the  work  was  the  same  as  for  that  in  Michigan  and  elsewhere— that  is, 
to  obtain  such  striking  contrasts  between  sprayed  and  unsprayed  trees 
that  they  would  form  long-remembered  object  lessons  for  all  who 
should  chance  to  see  them. 

The  spray  work  of  the  Ohio  Agricultural  Experiment  Station  after 
1890  was  quite  extensive:  but  the  treatment  of  peach  leaf  curl  is  not 
mentioned  in  the  bulletins  on  orchard  spraying  published  b}'  that 
station  in  December,  1891,  and  February,  1893,^  although  in  the 
latter  (Bui.  No.  -18.  p.  12)  the  spraying  of  peach  trees  for  other 
diseases  is  considered.  In  the  spring  of  1893,  however.  Prof.  W.  J. 
Green  sprayed  a  considerable  number  of  young  peach  trees,  just 
planted,  the  object  being  ""to  determine  the  truthfulness  of  the 
statements  that  had  been  made  concerning  the  effect  of  spraying  upon 
peach  trees."  In  relation  to  curl.  Professor  Green  says  that  he  "did 
not  see  any  effect  until  the  season  of  1894."  during  which  and  in  1895 
"there  was  some  effect  noticeable.""  He  saj'S  further,  in  this  connec- 
tion: "I  am  aware  that  other  work  in  this  direction  had  been  done 
before  I  commenced,  because  I  received  my  suggestions  from  some 
other  source,  but  I  can  not  now  recall  the  particular  case."'  (Letter 
dated  September  30,  1899.) 

Upon  these  results  obtained  by  Professor  Green,  and  supported  by 
the  work  of  Benton  in  California  and  Taft  in  ]Michigan,  were  based 
the  subsequent  experiments  of  Prof.  A.  D.  Selby  in  the  orchard  of 
"William  Miller,  of  Gypsum,  Ohio."  These  experiments  were  begun, 
according  to  Professor  Selby,  in  April,  1895/  but  no  results  with 
leaf  curl  were  obtained  until  1896.*  as  in  1895  there  was  no  difference 
between  sprayed  and  unsprayed  trees  in  the  amount  of  curl  developing, 
it  being  so  insignificant  as  to  be  without  evident  eff'ect.  The  curl 
which  developed  in  1896  enabled  iSIr.  Selby  to  obtain  some  contrasts 
between  sprayed  and  unspra3^ed  trees,  but  these  contrasts  were  not  as 

^ Green,  W.  J.,  The  Spraying  of  Orchards,  Ohio  Agr.  Exp.  Sta.  Bui.  No.  9,  Dec, 
1891,  Vol.  IV,  second  series;  Bui.  No.  48,  Feb.,  1893,  p.  12;  and  a  letter  from  Pro- 
fessor Green,  dated  "Wooster,  Ohio,  Sept.  30,  1899. 

'Letter  from  Prof.  A.  D.  Selby,  dated  Wooster,  Ohio,  Sept.  13,  1899. 

='L.  c;  also  Ohio  Agr.  Exp.  Sta.  Bui.  No.  92,  JNIarch,  1898,  pp.  237-245. 

*Ohio  Agr.  Exp.  Sta.  Bui.  No.  92,  March,  1898  p.  245;  also  Thirtieth  Ann.  Kept. 
Ohio  State  Hort.  Soc,  pp.  87. 


HISTORY    OF    TREATMENT.  63 

marked  as  they  would  have  been  had  the  disease  developed  seriously.^ 
As  it  was  light  in  18i>5  and  181H),  no  gain  in  fruit  was  shown  by 
sprayed  over  unsprayed  trees  these  years.  In  1897  the  work  was  con- 
tinued, and  owing  to  the  serious  development  of  curl  the  desired 
contrasts  in  foliage  were  obtained.  Unfortunately,  however,  the  fruit 
buds  had  been  killed  by  cold  and  no  fruit  records  were  obtainable. 
The  first  contrasts  in  fruit  on  sprayed  and  unsprayed  trees  in  ]\Ir. 
Miller's  orchard  were  reported  to  Mr.  Selby  in  18U8,  and  they  are 
both  valuable  and  conclusive.' 

The  announcement  of  the  Department's  work  on  leaf  curl  was  sent 
to  the  growers  of  peaches  in  Illinois,  Indiana,  and  Pennsylvania  at  the 
same  time  that  it  was  sent  into  Ohio  and  other  States  of  the  East,  viz, 
in  November,  1893 :  and  during  the  winters  of  1893-9-1  and  1894-95, 
135  peach  growers  in  Pennsylvania,  81  in  Indiana,  and  36  in  Illinois 
were  requested  to  spray  for  th6  control  of  curl  and  report  to  the 
Department.  A  complete  plan  for  these  tests,  control  trees  being 
provided  for  in  every  case,  was  sent  to  each  of  the  growers.  So  far 
as  reported,  where  instructions  were  followed,  the  results  of  this  work 
were  satisfactory  in  all  cases  where  curl  developed  and  where  frost 
did  not  prevent  the  obtaining  of  results. 

"Winter  spraying  for  the  control  of  curl  began  in  New  York,  so  far 
as  known  to  the  writer,  in  the  winter  of  1893-94,  during  which  and 
the  following  winter  over  seventy  peach  growers  of  the  State  received 
from  the  writer  full  instructions  for  the  treatment.  These  instruc- 
tions were  sent  out  through  personal  correspondence  with  orchardists 
in  over  twenty  of  the  peach-growing  centers,  and  by  means  of  care- 
fully prepared  circulars.  Among  others,  Mr.  W.  T.  Mann,  of  Barkers, 
undertook  sprav  work  for  the  Department  in  the  winter  of  1893-94. 
Carefulh^  planned  experiments  were  carried  out  by  him  in  his  young 
orchard,  the  spraying  being  done  on  April  9,  and  before  growth 
started,  and  alternate  rows  being  left  untreated  for  comparison.  Mr. 
Mann  reported  the  results  of  this  work  as  satisfactory,  and  thev  are 
elsewhere  given  in  this  bulletin.  Mr.  James  A.  Staples,  of  Marl- 
boro, also  conducted  spray  work  for  the  Department  in  1894,  1895, 
and  1896,  and  where  the  instructions  were  carried  out  respecting 
the  time  of  first  spraying  his  results  were  fully  satisfactory.  Prof. 
L.  H.  Bailev^  reported  the  work  of  Mr.  Henry  Lutts,  of  Youngstown, 
for  the  spring  of  1894;  and  Mr.  A.  D.  Tripp,  of  North  Ridgewa}', 
reports  excellent  results  from  his  work. 

'Ohio  Agr.  Exp.  Sta.  Bull.  No.  92,  pp.  246,247. 

^Ohio  Agr.  Exp.  Sta.  Bull.  Xo.  104,  March,  1899,  p.  210;  also  Rept.  Ohio  State 
Hort.  Soc,  1898,  p.  13. 

^Bailey,  L.  H.,  Impre!=i=ion.«  of  the  Peach  Industry  in  Western  New  York,  Cor- 
uell  Agr."  Exp.  Sta.  Bull.  No.  74,  Oct.,  1894,  pp.  382, 383. 


64     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

A  bulletin  of  the  Cornell  Agricultural  Experiment  Station,  by 
Georo-e  F.  Atkinson,^  which  appeared  in  September.  1894,  treats  of  leaf 
curl  and  plum  pockets.  Respecting  the  treatment  of  leaf  curl,  Mr. 
Atkinson  says  that  some  experiments  had  been  made  in  various  places 
by  spra^'ing  the  trees  with  Bordeaux  mixture  for  the  prevention  of  the 
disease.  Some  of  the  experimenters  regard  it  as  certain,  he  states, 
chat  the  disease  can  to  some  extent  be  checked  by  this  method,  and 
adds;  **  It  is  quite  likely  that,  in  some  cases  at  least,  another  disease 
is  confused  with  leaf  curl,  and  this  fact  might  account  in  those  instances 
for  the  results  claimed."  The  doubts  here  expressed  as  to  the  results 
of  the  work  in  New  York  do  not  appear  to  have  been  supported  bvany 
held  work  of  the  station ,  and  may  have  arisen  from  Mr.  Atkinson's  under- 
standing of  the  perennial  habits  of  the  fungus  causing  the  disease. 
There  seems  to  have  been  no  winter  spraying  for  curl  by  the  Cornell 
Station  before  the  spring  of  1898,  and  the  results  then  obtained  are  in 
perfect  accord  with  those  obtained  in  1894  by  growers  cooperating 
with  the  Department.  In  the  spring  of  1898  several  experiments  were 
instituted  and  carried  out  by  B.  M.  Duggar  and  H.  P.  Gould.  The 
results  of  this  work  are  given  in  a  bulletin  by  Mr.  Duggar,  published 
in  February.  1899.^ 

The  efforts  to  control  peach  leaf  curl  by  winter  sprays  in  Canada, 
so  far  as  concerns  the  work  of  the  Canadian  Government,  appear  to 
have  begun  nearly  simultaneously  in  Ontario  and  British  Columbia. 

At  the  experiment  farm  at  Agassiz,  British  Columbia,  the  peach 
orchard  had  suffered  severely  from  curl  prior  to  the  introduction  of 
winter  spraying.  The  su]:)erintendent,  Mr.  Thomas  A.  Sharpe, 
reported  for  1892  that  of  the  large  number  of  peach  varieties  at  that 
time  on  the  farm — about  116 — onlv  5  escaped  leaf  curl,  and  the  attack 
was  severe.^  In  the  report  for  1893  it  is  said  that  leaf  curl  was  worse 
that  year  than  ever  before.  Of  about  129  varieties  on  the  farm  the 
Malta  was  the  only  variety  on  the  level  land  that  was  entirely  free.* 
In  the  spring  of  1894  the  trees  were  sprayed  with  strong  Bordeaux  mix- 
ture when  the  leaves  were  partly  expanded,  but  no  leaf  curl  developed 
that  year,  even  the  unsp rayed  orchards  not  being  troubled  by  it.' 
It  should  be  stated  here,  however,  that  the  work  done  was  too  late  to 
have  given  good  results  had  curl  developed,  and  that  it  did  not  properly 
constitute  a  preventive  spraying.  Whether  this  late  sprajdng  was 
owing  to  the  nature  of  the  season,  or  whether  it  was  supposed  that 
such  treatment  w^ould  control  the  disease,  is  not  known  to  the  writer. 

1  Atkinson,  Geo.  F.,  Leaf  Curl  and  Plum  Pockets,  Cornell  Agr.  Exp.  Sta.  Bull. 
No.  73,  Sept.,  1894,  pp.  324-326. 

'^Duggar,  B.  M.,  Peach  Leaf  Curl,  etc.,  Cornell  Agr.  Exp.  tr^ta.  Bull.  No.  164,  Feb., 
1899,  pp.  377-384. 

» Kept.  Exp.  Farms,  1892,  p.  278. 

*  Kept.  Exp.  Farms,  1893,  pp.  342,  343. 
/Kept.  Exp.  Farms,  1894,  p.  404. 


HISTORY    OF   TREATMENT.  65 

In  1895  Mr.  Sharpo  reports  that  the  peach  trees  at  Agassiz  were 
sprayed  with  Bordeaux  mixture  before  leafing  out,  and  again  when 
the  leaves  were  nearly  full  grown.  He  states  that  the  sprayed  trees 
had  very  little  curl,  and  made  a  very  strong  and  healthy  gi'owth,  while 
on  a  few  unsprayed  trees  of  several  varieties  the  leaves  were  nearly 
all  destroyed  by  curl,  and  the  trees  themselves  made  a  very  feeble 
growth.^ 

This  treatment,  so  far  as  known,  is  the  first  successful  experiment 
for  the  control  of  curl  by  the  Canadian  Government.  Leaving  con- 
trol trees  for  comparison  added  greatly  to  the  value  of  the  work, 
which  was  also  strengthened  by  the  results  at  Agassiz  the  following 
3"ear,  1890.^  The  writer  regrets  to  add,  however,  that  unfavorable 
results  attended  the  spray  work  at  Agassiz  in  1898.^  The  reasons 
for  this  failure  are  not  apparent. 

In  Ontario  the  early  results  were  not  so  satisfactory  as  at  Agassiz, 
owing  to  the  nondevelopment  of  the  disease  in  Ontario.  Mr.  John 
Craig,  horticulturist  of  the  Central  Experimental  Farm,  at  Ottawa, 
planned  the  Ontario  work.  He  states  that  the  work  on  peaches  in 
189'±  was  planned  to  prevent  the  rotting  of  fruit  and  injury  from 
insects,  and  that  the  first  spraying  was  not  given  until  May  1.*  Mr. 
Craig's  work  on  leaf  curl  began  in  1895,  by  the  application  of  winter 
spraj's,''  but  owing  to  the  absence  of  the  disease  that  3'ear  no  con- 
clusive results  were  obtained.  Later  work,  I  am  informed  by  Mr. 
Craig,  has  given  more  conclusive  and  satisfactory  results.*  The  vari- 
able results  reported  in  Bulletin  No.  1,  second  series,  leads  the  writer 
to  wonder,  however,  if  the  early  spray  work  was  done  with  sufficient 
thoroughness.  Mr.  W.  M.  Orr,  of  Fruitland,  Ontario,  met  with  verj^ 
convincing  and  satisfactory  results  from  winter  spraving  in  1898.^ 
The  same  is  true  for  the  experiments  of  Mr.  A.  H.  Pettit,  of  Grimsby, 
Ontario,  who  carried  on  work  in  1898  and  1899,  the  results  of  the  latter 
year,  when  one  row  of  trees  was  left  untreated  for  comparison,  being 
very  striking. 

The  work  of  this  Department  in  extending  the  use  of  sprays  for 
the  control  of  curl  on  the  Pacific  coast  began  in  the  spring  of  1893. 
In  the  fall  of  that  year  a  circular  letter  on  the  subject  was  addressed  to 
many  Pacific  coast  growers,  and  this  was  closely  followed  by  requests 
that   growers    undertake   preventive   spray   work   in    the    winter  of 

^  Kept.  Exp.  Farms,  1895,  p.  396. 
2  Kept.  Exp.  FariiiP,  1896,  p.  449. 
'Eept.  Exp.  Farms,  1898,  p.  403. 
*Rept.  Exp.  Farms,  1894,  pp.  110,  111. 

^  Peach  Culture   in  Canada,  Bull.  No.  1,  second  series,  pj).  35-37;  Central  Exp. 
Farm,  Dept.  of  Agr.,  Ottawa,  Canada,  Sept.,  1898. 
^Letter  dated  Ottawa,  Oct.  7,  1897. 
'Canadian  Horticulturist,  Jan.,  1899,  pp.  18-20. 
19093— No.  20 5 


66     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

1803-94.  During  the  winters  of  1893-94  and  1894-95  the  writer  sent 
full  instructions  for  preventing  curl  by  winter  sprays  to  over  two 
hundred  and  seventy  California  peach  growers,  and  requests  to  carry 
on  spraying  experiments,  with  similar  instructions,  to  more  than  one 
hundred  growers  in  Oregon,  and  to  many  in  Washington.  In  all  of 
this  work  for  the  extension  of  spraying  an  effort  was  made  to  intro- 
duce it  in  as  large  a  number  of  leading  peach-growing  centers  as  pos- 
sible, especially  in  those  sections  of  the  coast  where  leaf  curl  had  been 
most  prevalent.  The  results  of  some  of  these  experiments  are  given 
in  Chapter  VII,  and  the  facts  gathered  and  experiments  conducted  under 
the  direct  charge  of  the  writer  in  1893,  1894,  and  1895  are  detailed  in 
full  in  other  portions  of  this  bulletin,  and  require  no  discussion  here. 


CHAPTER  IV. 

PLAN    OF    PREVENTIVE    SPRAY    WORK   CONDUCTED    BY    THE 

DEPARTMENT. 

PRELIMINARY    PLANS    FOR   THE    WORK. 

The  partial  control  of  peach  leaf  curl  in  the  spring  of  1893,  in  a  few 
orchards  of  the  Sacramento  Valle}^  in  which  the  trees  had  received  a 
winter  spraying  for  the  control  of  the  San  Jose  scale  {A><pidiottis  per- 
meio.vts),  showed  to  the  writer  the  importance  of  conducting  careful 
experiments  for  the  prevention  of  curl.  As  a  foundation  for  experi- 
mental work  a  circular  of  inquiry  was  sent  to  some  1,500  peach  growers 
of  the  United  States  in  the  fall  of  1893.  The  facts  thus  obtained  were 
of  much  value,  but  the  general  lack  of  accurate  knowledge  respecting 
both  the  nature  and  control  of  the  disease,  as  well  as  the  heavy  losses 
reported  from  this  cause  in  different  sections  of  the  country,  strikingly 
emphasized  the  need  for  widespread  and  thorough  preventive  experi- 
ments. 

After  careful  consideration  it  was  concluded  to  inaugurate  two  series 
of  experiments.  The  first,  which  had  been  planned  before  the  sending 
out  of  the  circular,  was  to  be  conducted  in  California  under  the  direct 
supervision  of  the  writer,  and  the  second,  planned  somewhat  similarly, 
though  on  a  more  limited  scale,  was  to  be  carried  out  by  the  growers 
themselves  in  various  peach-growing  sections  of  the  country.  The 
personally  conducted  work  is  described  here,  while  the  results  of  the 
cooperative  work  are  given  farther  on. 

Observation  and  correspondence  had  already  shown  which  sections 
of  California  were  most  subject  to  frequent  and  serious  recurrences  of 
the  disease.  Facts  thus  gathered  led  to  the  opening  of  correspondence 
with  Mr.  George  F.  Ditzler,  the  manager  of  the  Rio  Bonito  orchard, 
situated  in  the  Sacramento  Valley,  in  the  bottom  lands  of  the  Feather 
River,  near  Biggs,  Cal.  I'his  orchard  is  the  propertv  of  the  Hatch  & 
Rock  Orchard  Company,  and  comprises  some  1,600  acres,  several 
hundred  of  which  have  as  fine  peach  trees  as  any  in  the  State.  Among 
the  varieties  of  peaches  in  this  orchard  is  a  large  acreage  of  I-/ovell 
trees.  The  Lovell,  it  was  learned,  while  presenting  as  thrifty  growth 
as  any  variety  in  the  orchard  during  years  when  curl  did  not  prevail, 
had  been  especially  subject  to  it  in  seasons  favorable  to  its  develop- 
ment, the    crop    of    this    variety,  which    would    amount    to    several 

67 


68     PEACH  LEAF  CUEL:  ITS  NATUEE  AND  TEEATMENT. 

thousand  dollars,  having  been  largely  lost  in  1893.  After  a  brief 
correspondence  Mr.  Ditzler  kindly  offered  to  allow  the  Department  to 
select  from  the  orchards  of  Lovell  peaches  a  block  of  several  hundred 
trees  of  exceptionally  uniform  and  vigorous  growth  and  especially 
suited  to  the  purposes  of  the  experiments  planned,  and  no  finer  or 
more  uniform  block  of  trees  has  ever  beeii  seen  by  the  writer  than 
that  eventually  selected  and  assigned  to  this  experimental  work.  It 
consisted  of  nearly  600  trees  at  the  southwest  corner  of  a  40-acre  block 
of  Lovells,  and  was  nearly  level.  The  soil  was  sandy  loam — deep, 
rich,  and  almost  uniform  in  quality.  The  trees  had  been  set  in 
orchard  less  than  five  years,  were  25  feet  apart  each  way,  and  had 
grown  so  vigorously  that  before  pruning  the  branches  met  between 
the  rows  in  many  cases,  thus  presenting  tops  of  exceptional  size  for 
trees  so  3^oung. 

The  experiments  planned  included  a  rectangular  block  of  the  orchard, 
20  trees  wide  from  east  to  west  by  29  trees  long  from  north  to  south. 
The  tract  selected  was  500  feet  east  and  west  by  725  feet  north  and 
south,  or  nearly  8^  acres  in  extent.  At  the  south  of  these  Lovells  is 
an  almond  orchard  of  the  same  age;  at  the  west  a  young  apple  orchard. 

Through  the  center  of  the  experiment  tract,  extending  from  south 
to  north,  was  planned  a  driveway,  thus  dividing  the  trees  into  two  long 
rectangular  blocks,  each  block  being  10  trees  wide  from  east  to  west, 
and  29  trees  long  from  north  to  south.  Each  cross  row  of  10  trees  was 
numbered.  The  south  10  trees,  forming  the  south  east-and-west  row 
on  the  east  side  of  the  driveway,  was  designated  1;  the  second  row 
from  the  south,  2;  the  third  row,  3;  etc.,  the  north  row  on  the  east 
of  the  driveway  being  row  29.  On  the  west  of  the  driveway  the 
south  row  was  30,  the  second  row  31,  etc.,  the  north  row  being  58. 
This  arrangement  gave  580  trees,  divided  into  58  rows  of  10  trees 
each,  one-half  of  these,  rows  1  to  29,  being  east  of  the  driveway  and 
the  other  half,  rows  30  to  58,  west  of  the  same.  This  arrangement 
may  be  fixed  more  clearly  in  the  mind  by  the  diagram  on  page  09. 

This  diagram,  in  addition  to  showing  the  arrangement  of  the  rows, 
as  already  described,  is  planned  to  represent  and  distinguish  the 
rows  which  were  to  be  treated  with  sprays  from  those  which  were  to 
be  left  untreated  as  check  or  control  trees  in  each  experiment.  The 
trees  of  the  rows  to  be  treated  are  represented  by  a  star  (*)  and  the 
trees  to  be  left  unsprayed  are  shown  by  a  circle  (°),  with  the  exceptions 
to  be  noted.  It  may  thus  be  seen  that  each  row  of  10  trees  intended 
for  treatment  has  at  its  side  10  untreated  trees  as  a  check  or  control 
row.  With  the  exception  of  rows  29  and  58  each  control  row  serves 
for  comparison  with  two  sprayed  rows,  one  on  either  side.  This 
method  of  contrasting  each  control  row  with  a  sprayed  row  on  either 
side  admitted  of  the  planning  of  38  experiments  in  the  block  of  58 
rows,  each  experiment  comprising  20  trees — 10  sprayed  and  10 
unspraj^ed,  in  two  immediately  adjoining  and  parallel  rows. 


PLANS    FOR    SPRAY    WORK. 


(')'.> 


After  locating  unci  iiunilH'ring  eacli  of  the  3(S  expcrinient.s  tt)  be 
tested  the  block  was  carefully  examined  to  determine  if  any  of  the 
trees  were  missing  or  so  injured  as  not  to  represent  entire  trees.  The 
results  of  this  examination  are  also  embodied  in  the  plat.  Where 
trees  were  missing  the  fact  is  shown  l)y  a  cipher  (0)  in  the  place  of  the 


West.  3 


5G 
55 
54 
§53 
52 
51 
50 
49 
48 
47 
46 
45 
44 
ii 
42 
41 
40 
39 
38 
37 
36 
35 
34 
33 
32 
31 
30 


S     7     6     5     4 
-Tree  numbers.- 


Nortli. 


3     2     1   10     9     8 


South. 


-Truo  nmiibers.- 


24§ 


East. 


♦Sprayed  in  1894  and  1895,  except  where  noted. 

"^Unsprayed  in  1894  and  189.5. 

§  Sprayed  in  1894  and  left  unsprayed  in  1895. 

tree,  but  it  was  found  that  only  two  trees,  both  from  row  39,  were 
wanting  in  the  block.  The  cross  (+)  in  row  35  represents  a  nectarine 
tree,  omitted  in  results  of  work.  In  cases  where  main  limbs  had  been 
broken  off  or  the  tree  otherwise  injured,  the  proportion  of  the  tree 
remaining  is  expressed  in  numerals,  i.  e.,  8  in  the  place  of  a  tree  indi- 
cates that  the  tree  was  eight-tenths  perfect,  5  that  it  was  live-tenths 


70 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


perfect,  etc.     As  will  be  seen,  however,  there  were  very  few  imperfect 
trees. 

In  all  the  following  calculations  of  fruit,  etc.,  these  few  discrepan- 
cies in  the  number  of  trees  are  carefully  taken  into  account  in  arriv- 
ing at  results  intended  for  comparison  with  other  rows.  The  amounts 
produced  by  the  trees  of  each  row  are  first  divided  by  the  number  of 
trees  actually  in  the  row  to  obtain  the  average  per  tree,  and  this 
amount  is  multiplied  by  10  to  obtain  the  amount  a  full  row  would 
yield  at  the  given  average.  By  reference  to  the  plat  it  may  be  seen 
that  the  trees  and  parts  of  trees  missing  amount  to  but  5.8  equivalent 
trees  for  the  entire  block,  that  51  of  the  58  rows  have  the  whole  com- 
plement of  10  perfect  trees,  and  that  the  missing  trees  or  parts  of 
trees  are  divided  among  the  remaining  7  rows. 

SPRAY    WORK    CONDUCTED   IN    1894. 

The  spray  tests  conducted  in  the  Rio  Bonito  orchard  in  1894 
included  the  application  of  sprays  prepared  according  to  3S  different 
formulae,  making  38  distinct  experiments.  Each  experiment  included 
two  adjoining  rows  of  10  trees  each,  one  sprayed  and  the  other 
unsprayed  for  comparison.  Of  these  38  experiments  11  involved  two 
sprayings  of  the  trees  treated  and  27  a  single  treatment.  All  treat- 
ments were  made  during  the  dormant  period  of  the  trees  and  varied 
in  date  from  February  1  to  March  6.  The  consideration  of  the 
preparation  of  sprays  for  this  work  will  be  discussed  in  a  subsequent 
chapter  devoted  to  that  subject,  as  will  also  the  methods  of  applica- 
tion, which  will  be  given  for  use  in  both  small  and  large  orchards. 

The  table  which  follows  is  prepared  to  show  as  concisely  as  possible 
the  arrangements  adopted  for  the  experiments  of  1894.  The  rows  of 
trees  once  treated  and  those  twice  treated  are  shown,  the  date  or  dates 
of  treatment  and  the  formula  or  formulae  used  in  each  case. 

Table  1. — Showing  the  formula  of  the  sprays  applied  in  1894,  dates  of  application,  and 

rows  treated. 


Row  No. 


Date  of 
spraying, 


Formulse  for  45  gallons  of  spray. 


Feb.  20 


Feb.  24 
/Feb.  16 
lFeb.  28 


Feb.  23 
Feb.  24 


Feb.  23 
/Feb.  20 
\Mar.    3 


Feb.  24 
Feb.  13 


Feb.  13 
/Feb.  26 
\Mar.    6 


15  lbs.  sulphur,  30  lbs.  lime,  10  lbs.  salt. 

Control  row. 
10  lbs.  sulphur,  20  lbs.  lime,  7  lbs.  salt. 
10  lbs.  sulphur,  20  lbs.  lime,  7  lbs.  salt. 
5  lbs.  sulphur,  10  lbs.  lime,  3  lbs.  salt. 

Control  row. 
5  lbs.  sulphur,  10  lbs.  lime,  3  lbs.  salt. 
15  lbs.  .sulphur,  30  lbs.  lime. 

Control  row. 
10  lbs.  sulphur,  20  lbs.  lime. 
10  lbs.  sulphur,  20  lbs.  lime. 
5  lbs.  sulphur,  10  lbs.  lime. 

Control  row. 
5  lbs.  sulphur,  10  lbs.  lime. 
20  lbs.  lime,  20  lbs.  salt. 

Control  row. 
20  lbs.  lime. 

45  lbs.  salt  (hot). 

46  lbs.  salt  (hot). 


SPRAY    WORK    OF    1894. 


71 


Table  1. — Shon>inf/  the  formu/ir  of  the  Hprayn  applied  In  1S94,  dates  of  application,  and 

rows  treated — Continued. 


Row  No. 


Date  of 
spraying 


Formuke  for  46  gallons  of  spray. 


17 

18 

Feb.  26 

19 

Feb.  27 

•20 

21 

/Feb.  it; 

\Feb.  20 

Feb.  21 

22 

23 

24 

fFeb.    6 

\Mar.    1 

Feb.  23 

25 

26 

27 

/Feb.     6 

\Mar.    1 

Feb.  26 

28 

29 

30 

Feb.     2 

31 

32 

Feb.     2 

/...do... 
\Mar.    2 

34 

35 

Mar.    3 

36 

Feb.  27 

37 

38 

Feb.  26 

39 

/Feb.     1 
\Feb.  28 

40 

41 

Feb.  23 

42 

/Feb.  14 
\Mar.    3 

43 

44  .   .. 

Feb.  24 

45 

Feb    27 

46 

47 

/Feb.   14 

48 

iMar.    3 
/Feb.   14 

49 

50 

Feb.  14 

51 

Mar.    3 

52 

53 

/Feb.  14 
\Mar.    6 
Feb.  27 

54 

55 

56 

Mar.    6 

.57 

....do   .. 

58 

Control  row. 

3  lbs.  copper  !<iilphate,  5  lbs.  sulphur,  10  lbs.  lime. 

2  lbs.  copper  sulphate,  5  lbs.  sulphur,  10  lbs.  lime. 

Control  row. 
5  lbs.  copper  sulphate,  5  lbs.  lime. 
5  lbs.  copper  sulphate,  5  lbs.  lime. 

4  lbs.  copper  .sulphate,  5  lbs.  lime. 

Control  row. 
4  lbs.  copper  sulphate,  5  lbs.  lime. 

3  lbs.  copper  sulphate,  5  lbs.  lime. 
3  lbs.  copper  sulphate,  5  lbs.  lime. 

Control  row. 

3  lbs.  copiier  sulphate,  2  lbs.  lime. 
2  lbs.  cojipcr  sulphate,  5  lbs.  lime. 
2  lbs.  copjHT  sulphate,  5  lbs.  lime. 

Control  row. 
2  lbs.  copper  sulphate,  3  lbs.  ammonia. 
Control  row. 

4  lbs.  copper  .sulphate. 
2  lbs.  copper  splphate. 

2  lbs.  copper  sulphate. 

Control  row. 

4  lbs.  copper  sulphate,  5  lbs.  soda,  3  lbs.  ammonia. 

3  lbs.  cop])er  sulphate,  10  lbs.  sulphur,  10  lbs.  lime. 

Control  row. 

5  oz.  copper  carbonate,  3  lbs.  ammonia. 
5  oz.  copper  carbonate,  3  lbs.  ammonia. 
5  oz.  copper  carbonate,  3  lbs.  ammonia. 

Control  row. 

5  lbs.  copper  sulphate,  10  lbs.  lime. 
0  pints  spray  solution. 

6  pints  spray  .solution. 

Control  row. 
0  lbs.  copper  .sulphate,  15  lbs.  lime. 
3  lbs.  copper  sulphate,  15  lbs.  lime. 

Control  row. 
8  pints  spray  solution. 
8  pints  .spray  solution. 
6  pints  .spray  solution,  3  lbs.  lime. 
6  pints  spray  solution,  10  lbs.  lime. 

Control  row. 
8  pints  spray  solution,  3  lbs.  lime. 
5  lbs.  sulphur,  5  Ib.s.  lime. 

Control  row. 
10  lbs.  spray  solution,  1  lb.  soap  (hot). 
8  pints  spray  solution,  1  lb.  soap  (hot). 
3  lbs.  copper  sulphate,  10  lbs.  lime. 

Control  row. 
8  pints  spray  solution,  2  lbs.  copper  sulphate,  10  lbs.  lime. 
5  lbs.  sulphur,  15  lbs.  lime. 

Control  row. 


The  spray  work  outlined  in  the  above  table  was  fully  completed  before 
the  opening  of  many  of  the  peacli  blossoms  in  the  spring.  Following 
this  work,  plans  were  laid  for  the  preservation  of  records  of  fruit 
thinned  from  the  trees,  etc. ,  should  peach  leaf  curl  develop.  As  the 
spring  advanced,  however,  it  became  evident  that  the  disease  would 
not  appear  to  any  serious  extent  in  that  portion  of  the  State  that  sea- 
son, it  not  being  sufficiently  severe  to  produce  a  contrast  either  in 
foliage  or  fruit  between  the  sprayed  and  unsprayed  trees,  hence  the 
action  of  the  sprays  applied  could  not  be  determined.  While  this  fail- 
ure to  arrive  at  the  results  hoped  for  in  1804  was  much  regretted,  the 
failm-e,  nevertheless,  led  to  the  acquisition  of  certain  facts  at  a  later 
date  which  are  of  prime  importance  to  the  orchardist  wishing  to  com- 
bat the  disease  with  sprays.  The  treatment  of  the  trees  in  181>4  made 
it  possible  when  the  work  was  resumed  in  1895  to  ascertain  if  the 


72  PEACH    LEAF    CURL:    ITS    NATURE    AND    TREATMENT. 

effects  of  one  year's  treatment  extended  to  the  crop  or  foliage  of  the 
second  year. 

While  peach  leaf  curl  did  not  develop  seriously  in  the  Sacramento 
Valley  in  1894,  it  prevailed  quite  extensively  in  other  portions  of  the 
United  States.  This  resulted  in  acquiring  facts  bearing  on  the  experi- 
ments for  1895  in  the  Rio  Bonito  orchard.  The  experiments  planned 
by  the  Department  and  carried  out  by  growers  in  the  East  and  in  the 
north  Pacific  States,  where  leaf  curl  developed,  showed  that  one 
thorough  spraying  during  the  dormant  period  of  the  tree  was  sufficient. 
The  experiments  of  1895  were  consequently  modified  from  those  of 
1894  in  respect  to  the  number  of  applications  made,  as  well  as  in  other 
respects  found  to  be  advisable. 

SPRAY   WORK    CONDUCTED   IN    1895. 

In  the  spray  work  in  the  Rio  Bonito  orchard  during  the  winter  and 
spring  of  1895,  the  same  block  of  Lovell  peach  trees  was  selected  as 
that  treated  the  previous  year,  and  in  each  case  the  same  unsprayed  or 
control  rows  were  left  as  in  1894.  In  1895  the  number  of  experiments 
made  in  this  block  was  38,  as  in  the  previous  year,  but  three  of  the  38 
rows  were  not  sprayed,  being  left  without  treatment  for  the  purpose 
of  observing  the  action  of  sprays  applied  in  1894  upon  the  crop  and 
foliage  of  1895.  These  three  rows  were  numbers  4,  24,  and  53,  each 
of  which  had  received  two  treatments  in  1894.  The  facts  thus  learned 
are  considered  farther  on.  The  spray  work  of  1895  included  but  a 
single  spraying  of  each  row  designed  for  treatment.  As  already  indi- 
cated, each  experiment  included  one  treated  and  one  untreated  row, 
each  row  having  10  immediately  adjoining  trees.  By  treating  one  row 
on  either  side  of  each  control  row  the  latter  served  as  a  contrast  row 
for  both  sprayed  rows.  By  referring  to  the  plat  of  the  block,  p.  69, 
this  arrangement  may  be  seen.  Row  1  is  sprayed;  row  2,  unsprayed; 
row  3,  sprayed.  These  three  rows  make  two  experiments — rows  1 
and  2  compared  make  the  first  experiment,  while  rows  3  and  2  com- 
pared make  the  second  experiment.  In  like  manner  rows  4  and  5  and 
5  and  6  make  two  experiments.  These  illustrations  will  be  sufficient, 
as  the  entire  block,  with  the  exception  of  the  three  rows  already 
noted,  was  treated  according  to  the  same  general  plan. 

In  considering  the  application  of  sprays  in  the  experiments  of  1895, 
the  nature  of  the  sprays  used,  the  formulae  according  to  which  they 
were  prepared,  the  location  of  the  rows  treated,  and  the  dates  of  appli- 
cation, as  well  as  the  location  of  the  control  rows  for  comparison,  are 
set  forth  in  the  table  which  follows.  That  the  reader  may  better  grasp 
the  nature  of  all  treatments  which  each  row  had  received  the  previous 
year,  the  formula?  for  the  sprays  applied  in  1894  are  placed  at  the  left 
of  the  treatment  given  the  same  rows  in  1895. 


SPRAY    WORK    OF    1895. 


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74 


PEACH   LEAF    CURL!    ITS    NATURE    AND    TREATMENT. 


iC  iC  iC  iC  lO  lO 


GENERAL    CONSIDERATION    OF    SPRAYS    APPLIED.  75 

The  methods  of  preparing  and  applying  the  sprays  used  in  1895  are 
considorod  in  sub.se(|iient  chapters.  In  each  case  an  effort  was  made  to 
do  thorough  work  in  applying  the  sprays,  l)ut,  as  is  true  with  all  such 
work  in  the  Held,  more  or  less  variable  results  could  not  be  avoided 
owing  to  the  weather  conditions  and  other  influences.  The  treatment 
was  given  the  85  rows  during  the  ten  days  immediately  preceding  the 
general  opening  of  the  flowers,  that  is,  at  the  close  of  the  dormant 
period  of  the  trees,  or  from  February  ^i)  to  IVlarch  5.  In  a  few  of 
the  more  forward  trees  a  small  percentage  of  the  flowers  had.  opened 
before  the  completion  of  the  work. 

GENERAL   CONSIDERATION   OF    SPRAYS   APPLIED. 

Several  distinct  types  of  sprays  were  tested  in  the  preventive  work 
on  curl  in  1895,  and  these  were  prepared  in  many  forms  and  propor- 
tions. The  two  fungicidal  bases,  copper  and  sulphur,  which  are  now 
recognized  in  all  countries  as  most  valuable  for  this  class  of  work, 
enter  into  the  composition  of  a  large  proportion  of  the  sprays  used, 
in  one  form  or  another. 

In  testing  sprays  considerable  weight  was  given  to  the  fact  that 
the  peach  tree  is  subject  to  the  attacks  of  certain  serious  insect  pests, 
prominent  among  which  is  the  San  Jose  scale,  and  that  a  spray  com- 
bining both  fungicidal  and  insecticidal  properties  would  often  prove 
of  greater  value  than  one  the  action  of  which  was  solely  fungicidal. 
Having  these  facts  in  mind,  and  knowing  the  demonstrated  value  of 
the  sulphur,  lime,  and  salt  spray  as  an  effective  remedy  for  the  San 
Jose  scale,  this  spray,  together  with  various  modifications,  was  tested 
and  compared  (rows  1,  3,  and  6).  Besides  quantitative  modifications 
of  the  spray,  tests  of  its  constituents  were  made  to  acquire  such  facts 
respecting  their  value  as  were  obtainable.  The  sulphur  and  lime 
united  were  tested  in  several  proportions  without  salt  (rows  7,  9,  10, 
12,  16,  51,  and  57).  The  lime  and  salt  were  tested  together  (row  13), 
and  the  lime  was  tested  separately  (row  44).  The  trial  of  a  strong 
salt  solution  was  made  the  previous  year  (row  16),  but  as  it  injured 
the  foliage  somewhat  it  was  omitted  in  1895.  Other  modifications 
of  the  sulphur  spray  were  prepared  by  adding  ditterent  fungicides, 
with  the  hope  of  increasing  its  fungicidal  action  without  detracting 
from  its  effectiveness  as  an  insecticide.  Sulphate  of  copper  was 
added  in  different  proportions  (rows  18,  19,  and  36),  and  the  addition 
of  iron  sulphate  was  also  tried  (row  56). 

The  copper  sprays  tested  for  leaf  curl  were  numerous  and  were 
variously  prepared  and  combined.  As  alread}'  said,  copper  sulphate 
was  added  to  the  sulphur  sprays,  but  it  was  most  extensively  used  in 
the  preparation  of  the  Bordeaux  mixture,  in  which  form  it  was  applied 
in  many  experiments  and  of  various  strengths  (rows  15,  21,  22,  25,  28, 
33,  41,  45,  and  54).     Copper  sulphate  with  ammonia  (eau  celeste)  was 


76     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

tested  (rows  27  and  80),  as  was  the  modified  eau  celeste,  composed  of 
copper  sulphiate,  sal  soda,  and  ammonia  (rows  35  and  39).  Two  experi- 
ments were  also  conducted  with  ammoniacal  copper  carbonate  (rows  32 
and  38). 

The  action  of  sulphide  of  potassium  was  tested  (row  47),  as  well  as 
sulphide  of  potassium  combined  with  milk  of  lime  (rows  42  and  48). 

Iron  sulphate  in  connection  with  lime  was  applied  in  one  experiment 
(row  50),  and,  as  already  stated,  was  also  used  in  connection  with 
sulphur  and  lime  (row  56). 

Of  the  three  rows  left  unsprayed  in  1895  (rows  4,  24,  and  53),  one 
(row  4)  had  received  two  applications  of  the  sulphur,  lime,  and 
salt  spray  in  1894;  another  (row  24)  had  been  twice  sprayed  in  1894 
with  Bordeaux  mixture;  and  the  third  (row  53)  had  received  two  spray- 
ings in  1894  with  a  hot  saponilied  solution  of  sulphide  of  potassium. 


Bull.  20,  Div.  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  VII 


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DESCRIPTION  OF  PLATE  VII. 

Sprayeil  and  unsprayed  C'rawfords  Late  trees  in  the  orcliard  of  Mr.  .\.  D.  C'ntts, 
Live  Oak,  Cal.  The  tree  seen  at  the  right  was  sprayed  with  hnie,  sulphur,  and  salt 
in  February,  1893;  that  at  the  left  was  unsi)rayed  and  was  denuded  of  foliage  and 
fruit  l)y  eurl.  (See  records  of  fruit  of  sprayed  and  unsprayed  trees  in  this  orchard, 
p.  141.)  The  trees  were  photographed  in  May,  after  most  of  the  curled  leaves 
had  fallen  from  the  unsprayed  tree.      (Compare  witli  I'l.  XX.) 


chaptp:k  v. 

INFLUENCE  OF  SPRAYS  ON  THE  VEGETATION  OF  THE  TREES. 

SAVINC    OF   FOLIAGE    FROM    INJURY   IJY    CURL. 

(PI.  VII.) 

The  effeotivenoss  of  the  winter  .sprays  diseussed  in  the  previous  chap- 
ter in  saving  the  foliage  of  peaeh  trees  from  injurv  )»y  peach  leaf  curl 
has  been  carefully  considered.  The  relative  importance  of  this  matter 
appears  from  the  fact  that  it  is  the  injury  from  the  loss  of  foliage  which 
is  responsible  for  the  ultimate  loss  of  the  fruit.  The  spray  work 
already  mentioned  was  completed,  in  1895,  about  the  close  of  the  first 
week  in  March.  From  this  time  on  the  flowers  ()p<Mied  rapidly,  and 
they  were  soon  followed  b}-  the  pushing  of  the  leaf  ))uds  and  the  com- 
plete resumption  of  the  vegetative  growth  of  the  year.  By  the  mid- 
dle of  April  the  trees  were  well  in  foliage,  while  peach  leaf  curl  was 
nearing  the  height  of  its  development.  B}^  the  2:2d  of  the  month 
the  contrast  between  healthy  and  diseased  foliage  on  the  sprayed  and 
imsprayed  trees  had  become  so  great  that  a  careful  estimate  was  made 
of  the  percentage  of  the  diseased  leaves  upon  every  tree  in  the  block. 

The  first  estimate  of  the  condition  of  the  foliage  was  made  to  deter- 
mine the  amount  and  percentage  of  disease  present  on  sprayed  and 
unsprayed  trees.  The  estimate  of  each  tree  was  calculated  upon  the 
basis  that  the  foliage  present  represented  100  per  cent,  and  the  amount 
of  badly  diseased  leaves  was  taken  as  a  certain  per  cent  of  the  leaves 
present  at  that  date.  Badly  diseased  leaves  were  considered  as  those 
seeming  to  have  sufficient  curl  present  to  cause  their  premature  fall 
from  the  tree.  The  ultimate  comparisons  of  sprayed  witli  unsprayed 
rows  are  not  based  upon  this  first  estimate  of  foliage  as  the  disease  was 
still  progressing.  The  parasite  was  still  in  the  vegetative  state,  few  of 
the  swollen  leaves  as  yet  showing  the  fruit  of  the  fungus,  and  still  fewer 
having  fallen  from  the  trees.  The  trees  sprayed  with  the  stronger 
sulphur  preparations  were  injured  somewhat  by  the  sprays,  many  of 
the  more  tender  twigs  being  killed.  This  delaved  the  leafing  of  these 
trees,  and  resulted  in  their  showing  rather  a  smaller  percentage  of 
diseased  foliage  at  the  time  this  estimate  was  made  than  would  have 
l)(HMi  the  case  had  the  leaves  pushed  earlier.  These  discrepancies 
influence  only  a  few  of  the  sprayed  rows.  In  other  respects,  it  is 
believed  the  numerous  influencing  conditions  would  apply,  so  far  as 

could  be  told,  with  equal  force  to  all  rows. 

77 


78 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


In  takiug  the  percentage  estimates  of  disease  shown  in  the  following 
table,  the  trees  were  examined  in  north  and  south  rows.  This  was 
done  so  as  to  work  across  the  lines  of  the  experiment  rows  rather  than 
with  them,  and  for  the  purpose  of  avoiding  any  influence  which  a 
knowledge  of  the  sprays  used  on  the  trees  estimated  might  be  thought 
to  exert. 

Table  4. — Eslimaied  j)ercentage  of  diseased  leaves  on  trees  April  22  and  23,  1895. 


Row  No. 


Percentage  of  diseased  leaves  estimated 
Apr.  22  and  23,  1895,  on  tree  No.— 


3. 

4. 

5. 

6. 

15 

10 

10 

10 

90 

85 

85 

90 

35 

40 

35 

30 

80 

80 

85 

85 

85 

85 

80 

90 

40 

50 

40 

45 

25 

30 

25 

35 

80 

85 

75 

70 

■US 

42 

25 

27 

40 

40 

35 

27 

90 

85 

85 

85 

15 

35 

34 

.50 

55 

40 

45 

,50 

78 

78 

75 

76 

8 

13 

16 

16 

30 

45 

37 

31 

85 

85 

87 

78 

33 

40 

29 

32 

13 

16 

25 

23 

90 

90 

90 

90 

Hi 

26 

17 

10 

15 

9 

16 

9 

SO 

85 

85 

80 

80 

85 

85 

.85 

12 

18 

27 

15 

85 

90 

90 

85 

17 

2] 

21 

15 

21 

30 

26 

24 

90 

90 

90 

87 

15 

15 

10 

15 

85 

,S5 

90 

85 

30 

,35 

30 

30 

10 

10 

5 

10 

85 

90 

90 

85 

15 

20 

12 

10 

10 

10 

15 

10 

70 

75 

75 

75 

40 

35 

25 

19 

18 

15 
80 

80 

80  82 

12 

13  20 

18 

.50 

55  55 

65 

80 

85  88 

85 

16 

30  30 

35 

12 

12  1  10 

11 

90 

90 

80 

90 

00 

50 

65 

70 

40 

38 

37 

38 

85 

85 

85 

80 

40 

50 

45 

42 

28 

25 

32 

30 

80 

80 

80 

85 

80 

80 

85 

85 

11 

12 

12 

20 

80 

80 

85 

80 

30 

25 

22 

9 

31 

32 

21 

20 

85 

90 

85 

87 

Average 
per  cent 
of  dis- 
eased 
leaves 

per 

tree  in 

sprayed 

rows. 


Average 
per  cent 
of  dis- 
eased 
leaves 

per 
tree  in 
control 
rows. 


1 

2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 
47 
48 
49 
50 
51 
52 
53 
54 
55 
56 
57 
58 


55  60 


35 
80 
47 
27 
80 
45 
60 
80 
11 
30 
82 
35 
23 
90 
10 
12 
90 
85 
15 
90 
23 
15 
88 
20 
80 
35 
10 
90 
12 
12 
65 
24 
15 
85 
13 
55 
85 
30 
12 
85 
75 
28 
86 
35 
35 
85 
80 
16 
82 
19 
15 
90 


13.5 


20 
80 

S5 

31.0 
O80.5 

30 
30 
80 

41.5 
28.5 

45 
36 

80 

35.0 
32.0 

47 
35 

80 

39.3 
45.5 

13 
25 
90 

11.4 
28.9 

60 
36 
90 

35. 5 
21.4 

9 

8 
85 
80 
10 

85 

12.7 
10.7 

""ii»2.b 
13.7 

17 
19 
90 

20.1 
23.7 

15 

85 

13.3 

30 
5 

85 

31.5 
9.0 

10 
10 
65 

13.7 
14.2 

10 

18 
78 

29.0 
20.3 

17 
60 

85 

15.7 
,55.0 

25 
13 

85 

26.5 
12.6 

75 
42 

85 

68.0 
36.3 

33 

28 
80 

40.8 
29.1 

85 
18 

87 

083.0 
14.6 

13 
11 

88 

20.8 
22.1 

87.5 


8.5.0 
'77.' ,5 
'84.'6 
'78.4 

82.2 
'89.6 
83.7 


80.5 


88.7 
'84.'6 


88.5 

'io.'o 
'so.'s 
'si.'s 
8.5.' 5 
',^.5.' 4 

'82."6 
'<H2.'4 
'88.'2 


a  Rows  sprayed  in  1894  but  left  unsprayed  in  1895. 


SAVING    OF   FOLIAGE.  79 

General  consideration  of  the  above  ta})lc  develops  some  .striking 
contmsts.  By  adding  the  figures  corresponding  to  the  average  per- 
centage of  diseased  leaves  on  the  trees  of  the  conti'ol  rows,  and  dividing 
this  amount  by  the  number  of  rows,  we  find  that  in  the  entire  block, 
containing  200  control  trees,  83.6  per  cent  of  the  leaves  were  badly 
diseased  at  the  date  of  this  estimate.  In  contrast  to  this,  the  total  of 
the  average  percentages  of  disease  shown  l)y  the  trees  of  the  sprayed 
rows,  divided  by  the  numl)er  of  sprayed  rows  in  the  block,  shows  the 
average  amount  of  disease  in  the  spray (^d  rows  to  have  been  26.2  per 
cent.  Evidently  this  average  is  nuich  above  the  pcuvcntage  of  disease 
shown  at  that  date  ])y  many  separate  rows,  as  it  included  the  rows 
treated  with  noneffective  sprays  as  well  as  those  giving  the  best 
results.  Adding  the  averages  of  rows  4,  24,  and  53  and  dividing  the 
amount  by  3  gives  82  per  cent  of  disease  as  the  average  of  the 
three  rows.  As  noted  in  the  table,  these  rows  were  not  sprayed  in 
1895,  but  were  left  in  order  to  ascertain  the  effects  of  the  sprays 
applied  to  them  in  1894,  and  the  average  of  disease  is  seen  to  be  prac- 
tically as  great  as  upon  rows  never  spra3^ed. 

From  the  date  of  this  first  estimate  the  progress  of  the  disease  in 
the  orchard  was  very  marked.  Within  the  next  two  weeks  the  fungus 
fruited  quite  generally  upon  the  swollen  leaves,  and  a  large  percentage 
of  the  worst  diseased  leaves  had  fallen  from  the  trees.  By  May  9 
the  contrast  between  sprayed  and  uusprayed  trees  had  quite  generally 
reached  its  highest  point,  and  any  irregularities  of  special  trees,  etc., 
could  no  longer  be  considered.  On  Ma}*  9  a  second  careful  estimate  of 
the  foliage  was  made.  In  this  work,  however,  it  was  impossible  to 
estimate  the  amount  of  disease  on  the  trees  as  compared  with  the  total 
amount  of  foliage  present,  as  had  first  been  done,  for  much  of  the 
diseased  foliage  had  alread}'  fallen.  To  avoid  this  diflicultj^  a  new 
method  of  estimating  was  adopted.  From  the  entire  l)lock  of  trees 
were  selected  two  rows,  Nos.  21  and  22,  which  showed  only  from  4  to 
6  per  cent  of  disease,  and  were  in  other  respects  in  perfect  foliage.  A 
careful  study  of  these  rows  was  made  to  get  a  clear  idea  of  the  con- 
dition of  a  tree  in  full  foliage  at  that  date,  and  with  these  types  in 
mind  each  tree  of  the  entire  block  was  carefully  examined.  An  esti- 
mate was  made  for  each  tree,  ])ased  on  the  twenty  typical  trees  studied, 
to  deteruline  the  per  cent  of  perfect  foliage  upon  it,  taking  the  amount 
which  should  be  upon  the  tree  at  that  date,  if  no  disease  existed,  as 
10(1  per  cent.  The  following  table  gives  the  results  of  this  work.  The 
percentages  in  the  last  colunm  represent  the  gain  in  leaves  of  spraj^ed 
trees  over  the  average  of  all  control  trees  in  the  block.  The  manner 
of  obtaining  these  percentages  is  discussed  on  page  85. 


80 


PEACH    LEAF    CURL  I    ITS    NATURE    AND   TREATMENT. 


Table  5. — Estimated  percentage  of  healthy  foliage  on  the  sprayed  andunsprnyed  treex  May 
9,  1895,  as  compared  with  the  amount  a  healthy  tree  should  have  at  that  date. 


Row  Na 


1. 
2 

s'. 

4. 

5. 

6. 

7. 

8. 

9. 
10. 
11. 
12. 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
20. 
21. 
22. 
23. 
24. 
25. 
26. 
27. 
28. 
29. 
30. 
31. 
32. 
33. 
34. 
35. 
36. 
37. 
38. 
39. 
40. 
41. 
42. 
43. 
44. 
45. 
46. 
47. 
48. 
49. 
50. 
51. 
55. 
53. 
54. 


Percentage  of  healthy  foliage  compared 
with  the  amount  the  tree  should  have, 
estimated  May  9,  1895. 

Tree  No.  — 


1. 

92 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

93 

93 

92 

94 

95 

92 

92 

93 

9 

10 

12 

9 

15 

10 

8 

13 

10 

90 

85 

80 

82 

85 

85 

85 

80 

90 

15 

8 

15 

10 

15 

20 

18 

20 

12 

10 

12 

12 

10 

18 

15 

15 

25 

10 

85 

65 

87 

80 

85 

60 

83 

78 

80 

95 

85 

90 

85 

m 

84 

87 

85 

90 

10 

i; 

13 

9 

12 

10 

12 

25 

20 

88 

75 

87 

80 

90 

80 

88 

80 

85 

90 

80 

88 

8:' 

90 

'o2 

87 

85 

89 

9 

8 

10 

20 

11 

20 

1(1 

10 

12 

92 

80 

r^s 

85 

SO 

,S0 

78 

72 

80 

87 

87 

75 

85 

65 

86 

85 

80 

70 

8 

10 

15 

IC 

21' 

i;:. 

20 

20 

12 

95 

89 

95 

90 

90 

88 

92 

88 

93 

92 

65 

80 

80 

8G 

{'- 

85 

85 

85 

20 

11 

12 

10 

s 

l.i 

10 

22 

10 

92 

85 

90 

85 

88 

86 

8;'. 

80 

85 

90 

85 

«) 

91 

85 

85 

77 

84 

75 

10 

9 

9 

8 

9 

10 

10 

10 

20 

97 

95 

97 

89 

92 

99 

96 

98 

98 

96 

96 

96 

90 

90 

98 

95 

96 

90 

8 

10 

14 

10 

8 

10 

8 

20 

9 

8 

9 

11 

9 

9 

9 

10 

7 

8 

89 

90 

92 

85 

88 

87 

96 

92 

85 

10 

10 

9 

'8 

10 

12 

11 

8 

9 

91 

92 

97 

87 

92 

91 

89 

85 

98 

87 

88 

96 

88 

85 

92 

84 

86 

95 

9 

10 

12 

10 

8 

13 

9 

8 

8 

96 

95 

92 

91 

90 

96 

90 

95 

82 

11 

18 

20 

20 

15 

22 

21 

23 

23 

65 

50 

55 

60 

65 

45 

45 

45 

45 

92 

92 

94 

94 

90 

90 

85 

95 

92 

9 

9 

16 

20 

16 

14 

15 

15 

10 

86 

90 

88 

92 

92 

90 

98 

95 

93 

65 

80 

85 

90 

75 

80 

50 

90 

75 

10 

13 

10 

12 

15 

15 

12 

12 

12 

65 

45 

68 

70 

70 

75 

80 

75 

70 

73 

82 

93 

(c) 

(c) 

92 

85 

86 

78 

15 

10 

10 

12 

10 

12 

15 

11 

10 

93 

92 

95 

85 

85 

80 

90 

78 

87 

45 

25 

45 

28 

45 

50 

45 

45 

48 

10 

12 

15 

10 

15 

18 

10 

18 

22 

78 

75 

80 

55 

65 

55 

40 

65 

40 

89 

89 

80 

90 

90 

95 

75 

87 

75 

11 

16 

13 

15 

25 

20 

8 

18 

15 

40 

40 

40 

45 

28 

45 

50 

45 

80 

70 

75 

55 

70 

65 

50 

45 

50 

.50 

9 

10 

20 

18 

20 

15 

10 

12 

15 

70 

65 

50 

60 

40 

50 

45 

65 

65 

80 

70 

75 

70 

70 

65 

55 

70 

65 

9 

10 

10 

10 

18 

12 

18 

10 

18 

20 

15 

18 

8 

15 

15 

10 

10 

15 

85 

87 

90 

70 

82 

85 

85 

80 

88 

9 

14 

10 

9 

15 

15 

10 

9 

10 

85 

80 

70 

75 

65 

90 

60 

75 

68 

70 

83 

65 

60 

75 

87 

80 

70 

70 

,H 

10 

11 

10 

12 

12 

11 

8 

10 

Average 
per  cent 

of 
healthy 
leaves 
per  tree 

in 

sprayed 

rows. 


92.3 


84.7 
a  14. 8 


76.8 
85.4 


83.1 

85.4 


81.0 
79.5 


90.0 
82.0 


84.7 
83.2 


95.9 
94.5 


a  9. 4 

89.8 


91.2 
89.3 


52. 5 
91.9 


91.8 

78.2 


70.3 
83.4 


87.0 
41.6 


58.8 
85.7 


38.8 
58.0 


57.0 

68.5 


014.8 
82.2 


75. 8 
74.8 


Average 
per  cent 

of 

healthy 

leaves 

per  tree 

in  control 


10.1 


14.5 
'i4."i' 

"ii's' 
'u.h' 
"ii's 
'i6.'7 

'V2'.2 


12.  2 


9.7 

"ig.'s 


14.2 

'ii's 
"ii's 
'ii.'.V 
"is.' 9 
'ii'i' 
"i3."6 
"ii.'s 
'io.'i 


Gain  in 
leaves  of 
sprayed 
trees  over 
average 
of  all  con- 
trol trees, 
expressed 

in 
per  cent. 


a  Trees  sprayed  in  1894,  but  unsprayed  in  1895. 
b  Gain  of  control  row  over  row  sprayed  in  1894. 
c  Tree  missing. 


The  comparison  of  some  of  the  general  facts  brought  out  in  the  esti- 
mates of  foliage  April  22  and  23  and  May  9,  1895,  shows  the  progress 
of  the  disease  during  that  time. 


SAVING   OF    FOLIAGE, 


81 


T.\BLK  t>. — Comparatire  jwrccntnge  of  diseased  foliage  an  sprayed  and  imspraijed  trees 
April  22  and  23  and  May  9,  1895. 


Trees  examined. 

April  22 
and 

23, 1895. 

May  9, 

1895. 

Avemge  per  cent  of  disease  on  the  trees  of  all  control  rows 

83.fi 
26.2 

82.0 

86.9 

Average  (ler  cent  of  disease  nn  the  trees  of  all  siiraved  rows 

21  2 

Average  jier  cent  of  disease  on  the  trees  of  the  three  rows  sprayed  in  1894,  but 
left  unspra ved  in  1895 

87  0 

Those  comparisons  show  3.3  per  cent  more  diseased  foliage  on  the 
control  trees  Ma}^  0  than  April  '2)1.  The  percentage  of  foliage  of  the 
spniyed  trees  showing  disease^  had  decreased,  howi^-er,  5  per  cent.  Of 
the  total  foliage  of  the  trees  sprayed  in  1894.  l)ut  left  unsprayed  in 
ISito.  T)  per  cent  more  was  diseased  at  the  second  date  than  at  the  first. 
These  figures  indicate  that  the  divergence  in  the  percentage  of  disease 
on  sprayed  and  unsprayed  trees  was  still  increasing  just  prior  to  the 
second  estimate.  The  second  estimate  may  thus  be  considered  as  taken 
before  any  of  the  trees  had  begun  to  recover  from  the  efiects  of  the 
disease.  The  time  of  maximum  contrast  was  the  true  time  to  make 
the  estimates,  and  it  is  believed  the  date  of  this  second  estimate  was 
certainly  not  too  late  to  fully  comply  with  this  requirement.  This 
belief  was  substantiated  b\'  a  third  partial  estimate  made  a  week  later, 
which  gave  in  general  very  similar  results  to  those  obtained  Ma}'  9. 
It  siiould  also  be  said  that  the  decrease  in  the  percentage  of  disease  on 
the  sprayed  trees  between  the  dates  of  the  first  and  second  estimates 
did  not  indicate  that  the  second  estimate  was  made  too  late,  or  after 
the  trees  had  begun  to  recover,  but  mereh'  that  the  leaf  buds  had  not 
fully  pushed  at  the  time  of  the  first  estimate.  This  is  further  shown 
by  the  fact  that  the  percentage  of  disease  was  still  increasing  on 
unsprayed  trees  up  to  that  time. 

Before  considering  the  action  of  individual  sprays  in  saving  the 
foliage  from  curl,  the  following  comparisons  are  given  of  the  action 
of  the  classes  of  sprays  used: 

Table  7. — Percentage  of  healthy  foliage  on  trees  differently  .sprayed. 


Percentages  of  healthy  foliage  .shown  by  trees  sprayed  with 
diflfercnt  cla-sses  of  spravs.  P2stimated  April  23  and  Mav 
9, 1895. 


Average  of  30  trees  sprayed  with  siilphnr,  lime,  and  .salt 

Average  of  70  trees  sprayed  with  snipluirand  lime 

Average  of  100  trees  sprayed  with  the  two  preceding  sulphur 
sprays 

A  verage  of  90  trees  sprayed  with  Bordeaux  mixture 

.\ verage  of  20  trees  si>rayed  with  eau  celeste 

Average  of  20  trees  sprayed  with  modified  eau  celeste 

Average  of  130  trees  sprayed  with  the  three  preceding  copper 
.sprays 

Average  of  20  trees  sprayed  with  ammoniacal  copper  car- 
bonate   

19093— No.  20 6 


ercentage     of 
healthy    foli- 
age Apr.  22 
and  23, 1895. 

ercentage     of 
healthy    foli- 
age  May  9, 
1895. 

ain  in  per  cent 
of    foliage 
from  Apr.  23 
to  May  9, 1895. 

PU 

C^ 

o 

71.4 

84.6 

13.2 

69.3 

80.0 

10.7 

70.3 

82.3 

12.0 

86.2 

89.6 

3.4 

83.3 

91.7 

8.4 

83.0 

87.6 

4.6 

84.2 

89.6 

5.4 

09.8 

01.4 

eyes'" 

9^  ^  .00 

O   S3    t.rH 

O-O^  >. 
•«       CSS 

36"- So 


8.4 


82 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


T.\BLE  7. — Percentage  of  It ecdthy  foliage  on  treea  differently  sprayed — Continued. 


Percentages  of  healthy  foliage  shown  by  trees  sprayed  with 
different  classes  of  sprays.  Estimated  April  23  and  May 
9, 1895. 


Percentage    of 
healthy   foli- 
age Apr.  22 
and  23, 1895. 

Percentage    of 
healthy   foli- 
age May  9, 

1895. 

Gain  in  percent 
of    foliage 
from  Apr.  23 
to  May  9, 1895. 

76.3 
59.2 

79.2 
32.0 

54.3 
73.5 
54.5 

82.0 
57.0 

75.8 
38.8 

49.8 
58.8 
79.5 

5.7 

6.8 

25.0 

'csio 


Average  of 

and  lime 

Average  of 

Average  of 

lime 

Average  of 
Average  of 

lime 

Average  of 
Average  of 


30  trees  sprayed  with  copper  sulphate,  sulphur, 

(a) 

10  trees  sprayed  with  iron  sulphate  and  lime 

10  trees  sprayed  with  iron  sulphate,  sulphur,  and 


10  trees  sprayed  with  sulphide  of  potassium 

20  trees  sprayed  with  sulphide  of  potassium  and 


10  trees  sprayed  with  milk  of  lime 

10  trees  sprayed  with  milk  of  lime  and  salt. 


2.2 
3.4 


4.5 
14.7 


o  Compare  text. 

The  table  shows  the  average  of  healthy  foliage  on  the  trees  sprayed 
■with  the  sulphur  sprays  (sulphur,  lime,  and  salt,  30  trees;  sulphur  and 
lime,  70  trees)  to  haye  been  82.3  per  cent  May  9.  The  average  on  the 
trees  sprayed  with  the  leading  copper  sprays  (Bordeaux  mixture,  90 
trees;  eau  celeste,  20  trees;  modified  eau  celeste,  20  trees)  was  89.6 
per  cent.  The  average  amount  of  healthy  foliage  saved  on  trees 
sprayed  with  a  combination  of  these  two  leading  classes  of  sprays 
(Bordeaux  mixture  added  to  the  sulphur  and  lime  sprays,  30  trees) 
was  no  greater  than  the  average  saved  by  all  sulphur  and  lime  .spra3's 
alone,  being  82  per  cent  as  against  82.3  per  cent  for  the  sulphur 
sprays.  This  result  was  a  surprise,  but  by  carefully  looking  into  the 
reason  it  would  seem  that  the  low  average  in  the  case  of  the  combined 
sprays  was  due  to  the  low  average  of  the  single  row  36,  while  the  high 
average  of  the  sulphur  sprays  arose  from  including  in  the  average  the 
results  of  those  sprays  which  contained  much  more  sulphur  than  was 
used  in  the  combined  sprays.  Notes  on  the  spray  applied  to  row  36 
show  that  considerable  sulphur  was  precipitated  in  cooking,  probabl}^ 
through  overheating,  and  for  this  reason  it  would  be  as  well  to  omit 
this  row  in  determining  the  average  saving  of  the  combined  spraj's. 
The  two  remaining  rows,  18  and  19,  sprayed  with  combined  sprays, 
showed  84.7  and  83.2  per  cent  of  healthy  foliage,  respectively — an 
average  of  83.9  per  cent.  The  formula  for  each  of  these  experiments 
contained  5  pounds  of  sulphur.  In  the  experiments  with  uncombined 
sulphur  sprays  there  were  four  formulfe  containing  5  pounds  of  sul- 
phur each.  The  average  per  cent  of  saving  of  these  four  experiments 
was  75. 3.  These  facts  show  that  when  the  amount  of  sulphur  was 
equal  there  was  an  average  gain  of  8.6  per  cent  in  healthy  foliage 
resulting  from  the  addition  of  Bordeaux  mixture  to  the  sulphur 
spra3^s. 

The  average  percentage  of  foliage  saved  by  the  use  of  the  ammo- 
niacal  copper  carbonate  (20  trees)  was.  May  9,  61.4.    As  the  ammoniacal 


SAVING   OF    FOLIAGE.  83 

copper  carbonate  sprays  used  contained  niueh  less  basic  copper  car- 
bonate than  the  other  copper  sprays  applied,  their  comparativeh^  low 
effectiveness  against  ciirl  is  fully  accounted  for,  and  for  this  I'eason 
they  were  not  included  when  (calculating  the  average  action  of  the 
copper  spra3^s  in  general.  The}^  were  outclassed  by  the  amount  of 
copper  used  in  the  other  sprays. 

The  foliage  saved  by  the  use  of  iron  sulphate  and  lime  (10  trees) 
was  but  57  per  cent  May  9.  This  shows  a  much  less  satisfa(!tory  action 
than  either  the  copper  or  the  sulphur  sprays.  The  iron  sulphate  com- 
bined with  the  sulphur  and  lime  sprays  showed  a  saving  of  foliage 
Ma}^  d  of  75.8  per  cent.  While  this  is  a  good  showing,  the  beneficial 
action  was  evidently  due  to  the  sulphur  of  the  spray  and  not  to  the 
iron,  and  the  result  was  even  below  the  average  obtained  bj'  the  sulphur 
sprays  alone,  or  equal  to  those  having  the  same  amount  of  sulphur. 

One  experiment  (10  trees)  was  made  with  sulphide  of  potassium,  but 
the  average  percentage  of  foliage  saved  by  this  spray  was,  May  9,  only 
38.8.  Sulphide  of  potassium  combined  with  milk  of  lime  (20  trees) 
showed  a  greater  saving  of  leaves,  being  49.8  per  cent,  but  as  the 
sulphide  alone  gave  a  saving  11  per  cent  lower,  and  as  milk  of  lime 
saved  as  high  as  58.8  per  cent,  it  is  questionable  if  the  lime  was  not 
the  more  active  agent  in  the  combination.  As  already  stated,  the 
milk  of  lime  applied  as  a  spray  (10  trees)  showed  a  saving  of  58.8 
per  cent  of  the  leaves,  which  was  quite  satisfactory  for  a  spray  con- 
taining none  of  the  standard  fungicides.  The  spray  prepared  from 
lime  and  salt  (10  trees)  gave  a  high  record,  the  healthy  foliage  May  9 
being  79.5  per  cent.  While  it  is  possible  that  the  fungicidal  action  of 
this  spray  may  be  somewhat  higher  than  that  of  milk  of  lime  alone, 
it  is  perhaps  more  probable  that  the  results  noted  arose  from  another 
influence.  It  was  learned  in  the  previous  year's  work  that  a  solution 
of  salt  injured  the  new  growth  and  tender  leaves,  and  it  is  thought 
likely  that  in  the  present  case  the  earliest  growth  and  that  which  first 
showed  disease  was  destroj'^ed  by  the  spray,  and  that  the  foliage 
estimated  was  a  new  and  somewhat  later  growth,  showing  much  less 
disease  than  the  first  foliage  would  have  shown.  It  would  be  well, 
however,  to  repeat  this  test. 

Some  interesting  facts  are  brought  out  by  the  preceding  table  in 
relation  to  the  continued  action  of  the  fungicides  used.  By  comparing 
the  first  column,  the  percentages  of  healthy  foliage  taken  April  22 
and  23,  with  the  second  column,  the  percentages  taken  May  9,  it  will 
be  seen  that  the  percentage  of  healthy  foliage  on  all  trees  spraA^ed 
with  the  sulphur  or  copper  sprays  increased  decidedly  between  the 
two  dates  of  estimate,  as  shown  in  the  third  column.  On  the  other 
hand,  the  action  of  the  weaker  sprays  was  overcome  b}"  the  disease, 
and  the  percentage  of  healthy  foliage  May  9  was  much  less  than  April 
23,  as  shown  in  the  fourth  eohunn.     These  weaker  sprays  checked  the 


84 


PEACH  LEAF  CURL  I  ITS  NATURE  AND  TREATMENT. 


action  of  the  fungus  at  lirst,  but  were  not  sufficiently  active  or  per- 
sistent to  prevent  its  gradual  increase  upon  the  trees.  An  apparent 
exception  to  this  in  the  case  of  the  sulphide  of  potassium  appears  to 
arise  from  the  fact  that  the  disease  was  never  greatly  ch(>cked  by  this 
fungicide,  the  amount  of  health}^  foliage  being  only  32  per  cent  April 
23.  Another  and  more  marked  exception  is  seen  in  the  trees  spra\'ed 
with  lime  and  salt  in  solution.  It  is  thought,  however,  that  the  tru(> 
explanation  of  this  exception  is  that  given  in  the  preceding  paragraph. 

What  has  been  stated  will  be  sufficient  to  indicate  the  comparative 
value  of  the  main  classes  of  sprays  used  in  these  experiments.  It  is 
shown  that  the  highest  degree  of  (effectiveness  in  saving  foliage  is 
possessed  by  the  copper  sprays,  that  the  sulphur  sprays  also  possess  a 
high  degree  of  fungicidal  activity,  and  that  where  Bordeaux  mixture 
is  added  to  the  sulphur  sprays  the  effectiveness  of  the  latter  is  some- 
what increased.  It  is  also  made  clear  that  sulphide  of  potassium, 
sulphate  of  iron,  and  several  other  sprays,  as  tested,  are  of  secondary 
value  in  this  work.  It  should  be  noted  that  the  average  saving 
obtained  from  the  use  of  the  sulphur  sprays  is  sufficiently  high  to  well 
warrant  the  use  of  these  sprays,  either  in  combination  with  Bordeaux 
mixture  or  alone,  in  cases  where  it  is  desired  to  use  a  spray  having 
both  fungicidal  and  insecticidal  qualities. 

It  will  now  be  advantageous  to  briefly  consider  the  h>ading  indi- 
vidual sprays  composing  the  classes  of  sprays  already  discussed,  in 
respect  to  their  action  on  peach  foliage  and  peach  leaf  curl.  The  fol- 
lowing table  gives  a  compact  presentation  of  the  number  and  nature 
of  these  sprays,  as  well  as  their  action  in  controlling  curl: 

Table  S. — Nature  and  courjionilion  of  spraijs  applied. 


Row 
No. 


('lasses  and  formula;  of  sprays  applied. 


Sulphur,  lime,  and  salt : 

1.5  lbs.  sulphur,  30  lbs.  lime,  10  lbs.  salt , 

10  lbs.  sulphur,  20  lbs.  lime,  5  lbs.  .salt 

.'■>  lbs.  sulphur,  10  lbs.  lime,  3  lbs.  salt , 

Sulphur  and  lime : 

15  lbs.  sulphur,  30  lbs.  lime 

10  lbs.  sulphur,  20  lbs.  lime 

10  lbs.  sulphur,  8  lbs.  lime 

6  lbs.  sulphur,   4  lbs.  lime 

5  lbs.  sulphur,  15  lbs.  lime 

5  lbs  sulphur,  10  lbs.  lime 

5  lbs.  sulphur,   5  lbs.  lime 

Bordeaux  mixture  and  sulphur  sprays  combined  : 

3  lbs.  copper  sulphate,  10  lbs.  sulphur,  20  lbs.  lime 
3  lbs  copper  sulphate,  5  lbs.  sulphur,  10  lbs.  lime 
2  lbs.  copper  sulphate,  5  lbs.  sulphur,  10  lbs.  lime 
Bordeaux  mixture : 

0  lbs.  copper  sulphate,  15  lbs.  lime 


CD  Oj 


< 


92.3 

S4.7 
76.8 

85.4 
83.1 
85.4 
82.0 
74.8 
81.  0 
68.5 

78.2 
84.7 
83.2 


S.C:  Ki 


607 
549 

488 

554 
536 
554 
528 
473 
520 
424 

499 
549 
637 


80 
60 
60 

60 
60 
60 
80 
60 
60 
60 

70 
80 
80 

100 


SAVING    OF    FOLIAGE. 


85 


Taule  8. — y<ihin'  iiml  cninjxtslfioii  of  sj)r(iiis  ajiji/iiil — ('(iiitiiinci 


Row 
No. 


Cliisst's  iuni  I'oiiiiiihu  of  spniys  !ii>i>lif<i. 


off 


.2 
a>  O 


.S  r;  sea 
03  w  «  O 


o-S- 


3  lbs.  copper  snlphato,  I'l  lbs.  lime 

5  lbs.  copper  sulplmto,  Id  lbs.  lime 

3  lbs.  eopjier  sulphati',  10  lbs.  lime 

3  lbs.  copper  sulphate,  10  ll)s.  lime 

5  lbs.  copper  sulphate,  h  lbs.  lime 

4  lbs.  copjier  sulphate,   h  lbs.  lime 

3  lbs.  copper  sulphate,  •')  lbs.  lime 

2  lbs.  copper  sulphate,   .">  lbs.  lime 

Eau  celeste : 

4  lbs.  copper  sulphate,  3  pints  ammonia 

2  ll)s.  copper  sulphate,  3  pints  amm'oniii 

Modified  eau  celeste: 

4  lbs.  copper  suliihato,  ,"i  lbs.  sal  soda,  3  pints  ammonia. 

2  lbs.  copper  sulph.ite. :'.  lbs.  sal  soda,2  pints  ammonia. 
Ammoniacal  rdjijicr  carbunate: 

6  ounces  ((ijiiier  carbonate,  3  pints  ammonia 

Soiuices  CI  ijiper  carbonate,  2  pints  ammonia 

Iron  sulphate  and  lime  : 

6  lbs.  iron  snliihate,  10  lbs.  lime 

Iron  sulphate,  suljihur,  and  lime  : 

.5  lbs.  iron  sul]iliate,  .t  lbs.  sulphur,  10  Dis.  lime 

Potassium  sulphide  .solution  : 

8  pints  ]Mitassinm  suljihide  .solution 

1'ota.s.siinu  sulphide  .solution  and  lime: 

12  pints  potas.sium  sulphide  solution,  10  lbs.  lime 

8  pints  potassium  sulphide  solution,   5  lbs.  lime 

Lime  and  salt : 

20  lbs.  .ime,  20  lbs.  salt 

Lime : 

20  lbs.  lime 


*91. 
87. 
Sh. 
82. 
95. 
94. 
89. 
89. 

91. 
t92. 

91 

83. 

70. 
.51 


*604 
6t)6 
556 
529 
634 
624 
588 
584 

598 
1606 

603 
539 

438 
302 

336 

480 

197 

344 
219 

509 

350 


80 
100 
90 
80 
100 
100 
80 
80 

SO 

tioo 

80 
80 

80 
60 

40 

40 

40 

50 
40 

60 

50 


*  Exceptional,  see  p.  87.  t  Outside  row,  next  to  driveway. 

The  above  table  is  planned  to  trive  for  each  experiment  the  t'ollowing- 
facts:  (1)  The  number  of  the  row  to  which  <^he  spray  was  applied;  (2) 
the  nature  and  amount  of  the  ingreditMits  used  in  each  cas«»;  (8)  the 
average  per  cent  of  healthy  foliage  shown  by  the  trees  of  the  row 
May  !•,  1805;  (4)  net  gain  in  healthy  foliage  iil)ove  the  average  per  cent 
of  health}'  foliage  produced  b}'  all  of  the  control  trees  of  the  block 
(200  unsprayed  trees),  and  which  is  expressed  in  })er  cent;  (5)  thrift 
of  uninfected  leaves  in  color,  texture,  and  .size.  The  figur(\s  under 
the  foui'th  head  were  obtained  in  the  following  mtuiner:  The  a\'erage 
percentage  of  healthy  foliage  of  all  the  ti"(M\sof  each  control  row  was 
first  jisctn-tained.  These  amounts  Avere  added  together  and  divided  l)y 
the  number  of  rows  (20)  to  obtain  the  ax'crage  percentage  of  healthy 
foliage  of  all  control  trees  of  the  block.  This  axcrage  was  13.06. 
From  the  average  percentage  of  each  sprayed  row  was  then  su])tracted 
the  average  of  all  control  trees  to  ol)tain  the  g:un  in  hetUthy  foliage 
of  each  sprayed  row.  This  net  gain  was  then  di\  ided  by  the  13. OH 
per  cent  of  th(>  .-ontrol  trees  to  obtain  tiie  net  gain  per  cent  of  each 
sprayed  row.  For  example,  take  row  1 :  !t2.3  7;  13.06  %  =Ti>.24  % 
gain;  79.24  %  ^13.06  %  .shows  the  net  gain   to  be  'fftJ  =  60T%  of  the 


86  PEACH    LEAF    CURL".    ITS    NATURE    AND    TREATMENT. 

average  amount  of  healthy  foliage  of  the  control  trees.  The  fifth  sub- 
ject, thrif  tiness  of  leaves,  is  discussed  in  the  next  general  head  of  this 
chapter. 

In  considering  the  saving  of  foliage  induced  through  the  use  of  the 
sulphur,  lime,  and  salt  sprays  (rows  1,  3,  and  6)  in  comparison  with 
the  average  saving  of  sprays  containing  an  equal  amount  of  sulphur 
but  no  salt  (rows  7,  9,  10, 16,  57,  12,  and  51),  there  appears  to  be  a 
slight  gain  in  favor  of  the  former  sprays.  The  average  saving  from 
both  classes,  taken  together  or  separately,  is  in  proportion  to  the 
amount  of  sulphur  contained  in  the  spray.  With  15  pounds  of  sul- 
phur the  average  net  gain  in  healthy  foliage  was  580  per  cent;  with 
10  pounds,  517  per  cent;  with  6  pounds,  528  per  cent;  and  with  5 
pounds,  480  per  cent. 

In  considering  the  combined  sulphur  and  copper  sprays  (rows  18, 
19,  and  36),  it  is  well  to  omit  comparisons  of  row  36,  on  account  of 
the  injury  caused  to  the  effectiveness  of  the  sprav  applied  to  it  through 
the  precipitation  of  a  portion  of  the  sulphur  in  boiling,  as  has  already 
been  noted.  Rows  18  and  19,  containing  3  pounds  and  2  pounds  of 
copper  sulphate,  respectively,  and  each  containing  5  pounds  of  sulphur 
and  10  pounds  of  lime,  show  a  gain  in  healthy  foliage  of  519  per  cent 
and  537  per  cent,  or  an  average  gain  of  513  per  cent.  The  average 
gain  from  the  sulphur  sprays,  which  contained  the  same  amount  of 
sulphur  but  no  copper,  was,  as  already  stated,  180  per  cent.  This 
shows  the  advantage  of  adding  the  copper  to  the  sulphur  sprays. 

In  the  table  the  experiments  with  the  Bordeaux  mixture  are 
arranged  according  to  the  amount  of  copper  and  lime  used  in  each. 
The  results  obtained  in  the  9  experiments  bring  out  some  valuable 
facts  respecting  the  most  desirable  proportions  of  copper  and  lime  to 
be  used.  Of  the  9  experiments  with  Bordeaux  mixture,  2  formula? 
contained  15  pounds  of  lime  each,  3  formuhe  10  pounds  each,  and  4 
formulae  5  pounds  each. 

By  comparing  rows  15  (6  pounds  copper  sulphate,  15  pounds  lime), 
41  (5  pounds  copper  sulj)hate,  10  pounds  lime),  and  21  (5  pounds  cop- 
per sulphate,  5  pounds  lime),  it  will  be  seen  that  there  was  a  gain  in 
healthy  foliage  of  589  per  cent,  566  per  cent,  and  634  per  cent,  respec- 
tively. Dividing  these  gains  by  the  number  of  pounds  of  copper  in 
the  respective  formulae,  which  may  be  fairly  done,  owing  to  the  nearly 
equal  amounts  of  copper  contained  in  each,  the  following  results  will 
.be  obtained: 

Per  cent. 
Row  15  (6  pounds  copper  sulphate,  15  pounds  lime^l  pound  copper   to  2.5 

pounds  lime)  shows  a  gain  of  foliage  per  pound  of  copper  sulphate  of 98 

Row  41   (5   pounds  copper  sulphate,  10  pounds  lime  =  1    pound  copper  to   2 

pounds  lime)  shows  a  gain  of  foliage  per  pound  of  copper  sulphate  of 113 

Row  21   (5  pounds  copper  sulphate,  5  pounds  lime  =  1  pound  copper  to  1  pound 

lime)  shows  a  gain  of  foliage  per  pound  of  copper  sulphate  of 127 


SAVING   OF    FOLIAGE.  87 

These  comparisons  indicate  a  decided  increase  in  activity  of  the 
spraj's  as  the  percentuoc  of  lime  is  lessoned — the  total  amount  of  cop- 
per remaining  the  same,  at  least  to  that  point  where  the  number  of 
pounds  of  copper  sulphate  and  lime  are  eciual.  The  formula)  contain- 
ing 8  pounds  of  copper  sulphate  can  not  all  be  compared  as  justly  as 
the  above  formuUe  have  been,  owing  to  a  difference  in  the  make  of 
copper  sulphate  used  on  row  33.  However,  rows  45  and  54,  each  hav- 
ing been  sprayed  with  a  formula  containing  3  pounds  copper  sulphate 
and  10  pounds  lime,  may  be  compared  with  row  25,  which  was  treated 
with  3  pounds  of  copper  sidphate  and  5  pounds  of  lime.  The  average 
saving  of  foliage  per  pound  of  copper  sulphate  in  the  former  two 
experiments  (10  pounds  lime)  was  180  per  cent.  The  saving  per  pound 
of  copper  sulphate  in  the  latter  experiment  (5  pounds  lime)  was  196 
per  cent.  These  comparisons  also  show  most  gain  in  foliage  per  pound 
of  copper  sulphate  where  least  lime  was  used. 

That  no  misconception  may  be  formed  from  the  preceding  com- 
parisons, it  is  w^ell  to  consider  that  the  sprays  were  applied  in  these 
cases  immediatel}'  before  the  opening  of  the  buds,  so  that  prompt  action 
of  the  copper  was  of  greater  importance  than  the  enduring  qualities 
of  the  sprays.  As  will  be  elsewhere  shown,  however,  the  endurance  of 
sprays  upon  the  trees  is  largely  increased  with  the  increase  of  the 
amount  of  lime  they  contain.  A  large  increase  of  lime  above  the 
absolute  requirements  for  the  Bordeaux  mixture  is  not  necessary  when 
the  spray  is  applied  so  near  the  date  of  the  opening  of  the  buds  that 
its  action  can  not  be  delayed  without  loss  in  effectiveness.  On  the 
other  hand,  if  the  spray  is  applied  at  an  earlier  date,  so  that  it  is 
required  to  withstand  weathering  for  a  longer  period,  a  considerable 
increase  in  the  amount  of  lime  may  be  an  advantage  in  increasing  its 
enduring  quality. 

The  amount  of  copper  sulphate  used  in  the  preparation  of  the  Bor- 
deaux mixture  varied  from  2  to  0  pounds  for  45  gallons  of  spra3\  Of 
the  nine  formulae  tested,  that  containing  5  pounds  of  copper  sulphate 
and  5  pounds  of  lime  (row  21)  gave  the  highest  gain  in  foliage  over 
the  average  healthy  foliage  of  the  control  trees,  or  634  per  cent. 
There  was  an  actual  average  saving  of  95.9  per  cent  of  the  spring 
foliage  of  the  10  trees  sprayed,  consequently  the  average  loss  of  foliage 
in  this  experiment  was  only  4.1  per  cent.  The  next  best  results  were 
obtained  with  the  spray  containing  4  pounds  copper  sulphate  and  5 
pounds  lime  (row  22).  This  spray  gave  a  gain  in  foliage  above  the 
average  produced  by  the  control  rows  of  624  per  cent.  The  average 
amount  of  foliage  saved  on  the  10  trees  was  94.5  per  cent,  showing 
that  all  but  5.5  per  cent  of  disease  had  been  prevented.  While  row  33 
shows  the  next  highest  saving  in  foliage,  these  results,  as  already 
indicated,  are  exceptional,  as  shown  by  comparison.  The  yield  of 
fruit  which  this  row  produced  also  shows  the  foliage  records  to  be 
exceptional,  and  they  may  properly  be  omitted  in  these  comparisons. 


88  PEACH    LEAF    CURL:    ITS    NATURE    AKD   TREATMENT. 

The  results  obtained  by  the  use  of  eau  celeste  and  modilied  eau 
celeste  were  very  satisfactory,  but  in  no  case  was  as  high  a  percentage 
of  foliage  saved  by  them  as  in  the  better  tests  with  Boi'deaux  mixture. 
The  exceptionally  high  percentage  of  foliage  saved  on  row  30  with  but 
2  pounds  of  copper  sulphate  may  be  in  part  due  to  the  fact  that  the 
row  was  an  exterior  one  of  the  Ijlock  and  next  to  a  driveway,  where 
the  trees  may  have  been  better  nourished  than  those  of  interior  rows. 
By  comparing  the  formula  used  on  row  27  with  that  used  on  row  35 
(each  containing  4  pounds  of  copper  sulphate)  it  will  be  seen  that  the 
saving  of  foliage  was  about  equal  with  eau  celeste  and  modified  eau 
celeste.  Comparison  of  these  results  with  those  shown  by  row  22, 
which  was  sprayed  with  Bordeaux  mixture  containing  the  same  amount 
of  copper,  will  show  that  the  latter  saved  the  highest  percentage  of 
foliage. 

Ammoniacal  coppei  carbonate  gave  less  satisfactory  results  than  the 
preceding  sprays,  probably  owing  to  insufficient  copper.  The  various 
results  given  by  the  other  sprays  tal)ulated  require  no  special  comment. 

Another  fact  is  made  evident  by  the  preceding  table.  Of  two 
formula3  of  the  same  class,  as  the  Bordeaux  mixtures,  one  containing 
more  of  the  fungicide  than  the  other,  the  percentage  of  foliage  saved 
for  each  pound  of  fungicide  will  be  the  greater  in  the  weaker  spray. 
Each  of  the  Bordeaux  mixtures  used  in  spraying  rows  21,  22,  25,  and 
28  contained  5  pounds  of  lime,  but  the  amounts  of  copper  sulphate 
used  were  5,  4,  3,  and  2  pounds,  respectively.  The  total  net  amount 
of  foliage  saved  by  these  sprays  and  the  net  saving  per  pound  of  copper 
sulphate  each  contained  may  be  thus  shown. 

Row  21:  5-poun(l  formula,  (3;)4  per  cent  saved;  per  pound  of  copper  sulphate,  127 
per  cent. 

Row  22:  4-poun(l  formula,  624  per  cent  saved;  ])er  pound  of  copper  sulphate,  156 
per  cent. 

Row  25:  3-pound  formula,  588  per  cent  saved;  per  pound  of  copjier  sulphate,  196 
per  cent. 

Row  28:  2-pound  formula,  584  per  cent  saved;  per  pound  of  copper  sulphate,  292 
per  cent. 

These  figures  show  a  gradual  decrease  of  the  total  per  cent  of  foliage 
saved  as  the  amount  of  the  fungicide  is  decreased,  but  a  decided  increase 
in  the  percentage  of  foliage  saved  per  pound  of  fungicide. 

COMPARISONS   OF   WEIGHT    AND   COLOR   OF   FOLIAGE  FROM   SPRAYED   AND 

UNSPRAYED   TREES. 

Besides  the  direct  loss  of  leaves  through  infection  by  Exoasem  defor- 
mans^ there  is  an  indirect  loss  through  the  retarding  of  growth  of  such 
foliage  as  has  not  been  directly  infected  by  the  fungus.  A  limited 
examination  of  this  matter  was  made  May  17  and  18,  1895.  Two 
typical  trees  were  selected  in  adjoining  rows,  one  of  which  had  been 


20,  Div,  Veg.  Phys    &  Patn.,  U.  S.  Dept    of  Agriculture. 


Plate  VIII. 


6   ■= 


DESCRIPTION  OF  PLATE  VIII. 

Experiments  at  Biggs,  Cal.  (Unsprayed.)  Looking  north  through  the  Lovell 
trees  from  row  28  of  the  experiment  block,  sliowing  the  nnsjirayed  trees  on  l)oth 
sides  as  they  appeared  IVIay  15,  1895,  in  the  unsprayed  orcliard.  These  should  be 
contrasted  with  the  two  sprayed  rows,  21  and  22,  shown  in  PI.  IX. 


Bull    20,  Div.  Veg^  Phys.  &  Path.,  U.  S,  Dept.  of  Agriculture. 


Plate  IX. 


DESCRIPTION  OF  PLATE  IX. 

Experiments  at  Biggs,  Cal.  (Bordeaux  mixture.)  Looking  east  between  rows  21 
and  22,  May  15,  1895.  Row  21  was  treated  before  blooming  with  5  pounds  copper 
sulphate,  5  pounds  lime,  and  45  gallons  of  water,  and  row  22  with  4  pounds  copper 
sulphate,  5  pounds  lime,  and  45  gallons  of  water.  Row  21  matured  4,443  pounds  of 
fruit,  and  row  22,  4,421  pounds,  while  row  20,  unsprayed,  just  south  of  row  21, 
matured  only  648  pounds,  and  row  2,3,  unsprayed,  just  north  of  row  22,  matured 
only  712  pounds.  Row  21  set  22,164  peaches,  and  row  22  set  21,478,  while  row  20 
set  only  1,911,  and  row  23  only  2,127;  or,  in  other  words,  row  21  set  eleven  times  as 
many  peaches  as  row  20,  and  row  22  ten  times  as  many  as  row  23  (p.  Ill) .  (Com- 
pare with  PI.  VIII.) 


COMPARATIVE    WEIGHT    AND    COLOR    OF    FOLIAGE.  89 

sprayed  and  tho  othor  not.  Those  were  trees  No.  10  of  rows  20  and 
21.  Tree  No.  10  of  row  21  was  sprayed  the  first  week  in  Marcli,  1895, 
with  Bordeaux  mixture  (5  pounds  copper  sulphate,  5  pounds  lime). 
Tree  No.  10  of  row  20  had  not  been  sprayed.  From  each  of  these  trees 
was  gathered  2  pounds  of  hoalthy  folia<*'e.  Careful  measurements 
wore  made  of  the  length  of  the  branches  of  1894  o-rowth  necessary  to 
yield  this  weight  of  healthy  leaves,  and  it  was  found  that  on  tho 
unsprayod  tree  it  required  18H  foot  2  inches,  while  on  the  sprayed  tree 
it  reijuired  only  -49  feet  4  inches.  The  work  was  done  as  similarly  as 
possible  on  both  trees.  The  2  pounds  of  foliage  from  the  sprayed 
tree  contained  2,428  leaves,  and  tho  2  pounds  from  the  unsprayed  tree 
2,546.  In  other  words,  118  more  healthy  leaves  were  required  from 
the  unsprayed  tree  than  from  the  sprayed  tree  to  equal  2  pounds  in 
weight,  or  59  more  leaves  per  pound.  This  result  is  due  to  the  indi- 
rect rather  than  the  direct  action  of  tho  disease.  The  leaves  from  the 
unsprayed  trees,  being  healthy,  should  average  as  great  in  weight  as 
those  from  the  sprayed  trees,  were  it  not  for  tho  retarding  and 
impoverishing  action  of  the  disease  upon  tho  general  growth  of  the 
tree.  In  comparing  diseased  with  healthy  loaves,  however,  this  ratio 
would  be  reversed.  Tho  number  of  diseased  leaves  required  for  a 
given  weight  would  be  much  less  than  the  number  of  healthy  leaves 
required.  The  diseased  leaves  are  greatly  curled  and  distorted  through 
the  irritation  or  stimulative  action  of  tho  fungus  present  in  tho  tissues, 
and  in  many  instances  thoy  also  become  enormously  increased  in  width, 
thickness,  and  weight. 

The  contrast  observed  in  the  color  and  general  appearance  of  the 
leaves  of  the  sprayed  and  unsprayed  trees  was  very  marked.  The 
foliage  of  tho  trees  treated  with  the  stronger  copper  sprays,  especially 
tho  Bordeaux  mixtures,  presented  the  finest  appearance.  On  May  8, 
1895,  t^vo  months  after  tho  spray  work  was  completed,  and  at  the 
height  of  the  disease,  the  foliage  on  trees  thus  sprayed  presented  the 
greatest  perfection.  It  was  so  abundant  and  so  dense  as  to  throw 
very  dark  shadows  beneath  the  trees,  making  it  difficult  to  obtain 
good  photographs  among  them.  This  dense  foliage  existed  upon  both 
the  lower  and  the  upper  ))ranches.  The  leaves  were  of  a  very  dark 
and  rich  green  color,  long,  soft,  and  beautiful.  Upon  the  unsprayed 
trees  comparatively  few  leaves  presented  the  appearance  of  full 
health,  and  much  of  the  diseased  foliage  had  already  fallen,  leaving 
many  trees  nearly  bare.  The  color  of  much  of  the  remaining  foli- 
age was  vellow  and  sickly.  Many  of  the  uncurled  leaves  were  small 
and  light  colored  on  both  tho  lower  and  the  upper  limbs.  What 
growth  these  trees  had  made  up  to  that  date  was  largely  terminal,  very 
little  healthy  or  comparatively  healthy  growth  being  apparent  from 
lateral  buds.     (Compare  Pis.  VIII  and  IX.) 


90     PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

The  influence  of  the  various  sprays  on  the  thriftiness  of  the  leaves 
was  especially  examined.  This  examination  was  conlincd  to  such  foliage 
as  was  free  from  infection  by  the  fungus,  but  was  extended  to  sprayed 
and  unsprayed  trees  alike,  and  to  all  rows  of  the  block.  In  recording 
the  comparative  thrift  of  uninfected  foliage,  attention  was  given  to  the 
depth  of  the  green  color,  to  the  softness  of  texture,  and  to  the  size  of 
the  leaves.  These  features  of  the  foliage  were  considered  collectively 
and  recorded  on  the  scale  of  100;  for  instance,  the  most  thrifty  foliage 
was  recorded  at  100  per  cent  of  thrift,  and  the  less  thrifty  at  a  lower 
percentage.  This  method  enables  one  to  distinguish  at  a  glance  those 
spra^^s  giving  the  l^est  results  in  color,  texture,  and  size  of  leaves — in 
other  words,  in  functional  ability.  The  records  for  each  row  and 
formula  are  given  in  the  general  table  under  the  preceding  head  of  this 
chapter,  to  which  the  reader  is  referred.  It  will  there  be  seen  that  the 
trees  of  5  rows  produced  foliage  of  the  highest  quality  in  spite  of  the 
presence  of  disease.  These  rows  were  all  sprayed  with  the  copper 
sprays,  and  all  but  one  with  Bordeaux  mixture.  Owing  to  the  fact 
that  row  30,  showing  lirst-quality  foliage,  was  an  outside  row,  it 
may  be  well  to  omit  it  in  comparisons.  The  remaining  -1  rows,  Nos. 
15,  41,  21.  and  22,  were  all  spraved  Avith  Bordeaux  mixture,  containing 
6  pounds,  5  pounds,  5  pounds,  and  4  pounds  of  copper  sulphate, 
respectively.  Smaller  amounts  of  copper  sulphate  did  not  give  equally 
high  results. 

The  average  results  shown  by  the  different  classes  of  sprays  are  as 
follows: 

Per  cent. 

Sulphur,  lime,  and  salt  (3  rows) 67 

Sulphur  and  lime  (7  rows) 63 

Bordeaux,  sulphur,  and  lime  combined  (3  rows) 77 

Bordeaux  (9  rows) 90 

Bordeaux,  4,  5,  and  6  pound  formulfe  (4  rows) 100 

Eau  celeste  (2  rows) 90 

Modified  eau  celeste  (2  rows) 80 

Ammoniacal  copper  carbonate  (2  rows) 70 

Iron  sulphate  and  lime  (1  row) 40 

Iron  sulphate,  sulphur,  and  lime  (1  row) 40 

Potassium  sulphide  (1  row) 40 

Potassium  sulphide  and  lime  (2  rows) 45 

Lime  and  salt  (1  row) 60  ^ 

Lime  (1  row) 50 

Trees  sprayed  in  1894,  but  not  in  1895  (3  rows) 20 

Control  trees  (19  rows) 20  - 

The  Bordeaux  mixture  is  here  shown  to  give  the  best  average  results 
as  to  thrift  of  foliage.  The  excellence  of  texture,  color,  and  size  of 
the  leaves  on  rows  sprayed  with  the  stronger  Bordeaux  mixtures 
would  be  hard  to  surpass. 

^  First  leaves  probably  injured  by  spray. 

^One  exceptional  row,  showing  40  per  cent,  omitted;  perhaps  benefited  by  wind- 
bome  spray. 


INFLUENCE    OF    SPRAYS    ON    THE  VEGETATION    OF  THE   TREES.       91 

GROWTH    OF    URANCHES   AND    LEAF    liUDS   ON    iSl'HAYEI)    AND    UNSPRAYED 

TREES. 

Besides  knowing  the  action  of  the  disease  and  of  the  sprays  upon 
foliage,  it  is  desirable  to  ascertain  their  action  on  leaf  buds  and  the 
growth  of  branches.  Two  months  after  growth  started — from  May 
10-1-ir,  1895 — a  study  was  made  of  the  growth  of  20  trees  in  the  experi- 
ment block,  10  sprayed  and  10  unsprayed.  The  rows  selected  for  this 
work  were  Nos.  20  (unsprayed)  and  21  (sprayed).  These  rows  were 
types  of  the  injurious  action  of  the  disease  and  of  the  beneficial  action 
of  the  spra}'  applied,  which  was  5  pounds  of  copper  sulphate  and  5 
pounds  of  lime.  Much  time  Avas  given  to  making  measurements  of  the 
new  growth  and  recording  the  results,  the  time  being  equalh'  divided 
between  the  10  sprayed  and  the  10  unsprayed  trees.  Typical  limbs 
were  nieasured^upon  both  the  lower  and  upper  portions  oT  the  tre^g7 
and  the  lenp-th  ni^cprnpTraTivp  henlth  of  the  new  growth^ was  recorded. 


The  length  of  1S*J1  growth  and  that  which  was  older  was  first  ascer- 
tained, and  was  followed  by  careful  measurements  of  all  spring  growth 
of  1895  arising  from  wood  of  1891  or  from  that  which  was  older.  The 
results  of  this  work  are  shown  in  the  following  table: 

Table  9. — Records  of  nieanurements  of.  healtlni  and  diseased  wood  on  unsprayed  and 
sprai/ed  trees,  taken  May  10-14,  1895. 


1 

•2 

3 

4 

5 

6 

7 

8 

9 

10 

Total 


Row  20,  unsprayed  trees. 


.^^ 


In. 
1,422 
1,614 
1,364 
1,304 
1,576 
1,8«6 
1.366 

1,7.T« 

1.986 
1,912 


16,188 


Length  of  spring  growth 
of  1895— 


On  wood  of 

1894. 


In. 
492 
.570 
301 
.5.57 
499 
298 
.527 
686 
977 
670 


In. 
249 
229 
251 
304 
326 
2.57 
230 
516 
550 
582 


5,577      3,494 


On  wood  more 

than  1  year 

old! 


Row  21,  sprayed  trees. 


Ooo 


In. 

76 
219 

83  I 
234  ; 

85  1 
182 

18 

53 
120 

56 


1,126 


91 
134 
22 
29 
41 
41 
32 


In. 
674 
664 
592 
666 
702 
976 
998 

1,068 
938 
982 


8,260 


Length  of  spring  groAVth 
of  1895— 


On  wood  of 
1894. 


In. 
1,189 
908 
768 
1,.580 
1,100 
1,2.59 
1,348 
2, 751 
2,100 
1,869 


In. 


14,872 


40 


On  wood  more 

than  1  year 

old. 


In. 
194 
494 

46 
330 

45 
325 
183 
195 

84 
220 


In. 


2,116 


From  the  footings  in  the  preceding  ta])le  it  appears  that  the  total 
length  of  1894  wood  measured  upon  the  unsprayed  trees  was  nearly 


twice  as  great  as  that  measured  on  the  sprayed  trees.  This  arose  from 
the  scarcity  oFliew  growth  on  this  unsprayed  woo5,  hence  an  equal 
time  given  to  taking  measurements  upon  each  tree  included  more  old 
wood  upon  unsprayed  than  upon  sprayed  trees. 


92 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


On  the  unsprayed  trees,  prior  to  the  middle  of  May,  the  total  amount 
of  new  growth  on  10,188  inches  of  189-1:  wood,  including  the  older  wood 
from  which  this  arose,  was  10,599  inches.  On  the  sprayed  trees  the 
new  growth  amounted  to  17,045  inches  during  the  same  time  (two 
months)  on  8.260  inches  of  189-4  growth,  including  the  older  growth 
from  which  the  latter  arose.  JThis  was  a  net  gain  of  215  per  cent, 
length  of  old  wood  considered,  over  the  growth  produced  by  the 
unsprayed  trees.  Otherwise^tatocl.  the  unspra^'i^d  trees  had  tneragecl 
a  new  spring  growtli  oF7  85  inches  \)ov  running  foot  of  1M*4  wood  and 
older,  while  the  sprayed  trees  had  produced  a  growth  of  2-1.75  inches 
per  foot  of  1891  wood  and  older  during  the  same  time.  This  shows 
a' gain  in  growth  on  the  sprayed  trees  during  these  two  months  of 
16.90  inches  per  foot  of  old  wood.  The  importance  of  this  matter 
will  appeal'  to  all  growers  who  have  peach  orchards  situated  where  the 
spring  growth  represents  the  major  part  of  that  of  the  season,  as  is 
true  in  man}''  peach-growing  regions.  In  such  orchards  this  would 
frequently  represent  a  reduction  of  25  per  cent  in  the  annual  growth. 
In  the  peach,  the  growing  wood  of  one  year  is  the  bearing  wood  of 
the  next,  hence  the  amount  of  wood  produced  would  have  added  sig- 
nificance. 

Considering  the  total  growth  of  the  spring  of  1895  from  wood  grown 
prior  to  1894 — the  pushing  of  dormant  or  quiescent  buds — an  analysis 
of  the  table  shows  a  net  gain  by  the  old  wood  of  sprayed  trees  of  173 
per  cent  above  the  growth  produced  from  like  wood  of  unspra3^ed 
trees.  This  action  of  spray  enables  the  grower  to  renew  bearing  wood 
on  the  lower  portions  of  his  trees,  which  is  an  advantage  where  trees 
are  old  or  close  set  and  tending  to  grow  upward,  or  where  curl  or  other 
causes  have  tended  to  denude  the  lower  limbs  of  3^oung  and  productive 
wood.  This  tendency  of  Bordeaux  mixture  to  aid  in  the  forcing  and 
active  growth  of  dormant  l)uds  was  especially  well  marked  in  the  case 
of  a  tree  sprayed  very  thoroughh^  on  one  side  (6  pounds  copper  sul 
phate,  1  pounds  quicklime,  45  gallons  of  water)  and  left  unsprayed  on 
the  other.  From  the  base  of  the  main  liml)s  on  the  spraj'ed  side  there 
arose  13  shoots  from  dormant  buds  during  the  first  two  months  of 
spring  growth,  while  the  unsprayed  limbs  produced  practically  none. 
The  13  shoots  on  the  sprayed  side  had  made  the  following  growth  to 
Ma}^  17,  growth  beginning  about  the  close  of  the  first  week  in  March: 


Shoots. 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

Total. 

Length  in  inches 

36 

44 

29 

37 

46 

21 

36 

36 

36 

46 

22 

21 

23 

36  feet  1  inch. 

As  shown  by  the  table,  the  growth  coming  from  13  dormant  buds 
at  the  base  of  the  main  limbs  of  the  spraj^ed  side  of  the  tree  during 
the  first  two  mouths  of  spring  growth  amounts  to  36  feet  and  1  inch, 


COMPARATIVE  GROWTH  OF  BRANCHES  AND  LEAF  BUDS.   93 

or  an  axeraov  ot"  ovrr  ;>;>  inclu's  tor  the  lo  shoots.  That  this  astonish- 
ing pushing  of  new  ))asal  buds  was  not  due  to  injur}^  of  the  top  by  the 
spray  was  shown  by  the  immense  amount  of  dark  grcM'n  foliage  the 
sprayed  half  of  the  tree  produced  and  from  the  amount  and  perfec- 
tion of  the  fruit  it  bore.  It  was  evidently  an  aided  or  stimulated  basal 
growth.  In  talde  U  is  shown  the  comparative  health  or  disease  of 
the  spi-ing  wood  measured.  Wiiere  shoots  liad  sult'ered  from  disease 
to  such  an  extent  that  they  were  enlarged,  crooked,  or  otherwise  dis- 
torted or  injured  l)y  the  disease,  they  were  classed  as  diseased ;  when 
not  so  injun^d,  they  were  classed  as  healthy.  In  respect  to  this  classi- 
iication  the  tal)le  gives  the  following  facts:  On  the  unsprayed  trees  the 
new  shoots  nieasun^d  on  growth  of  1894  or  older  amounted  to  10,599 
inches,  of  which  0.703  inches  was  of  healthy  wood  and  3,896  inches 
of  diseased  wood,  or,  in  other  words,  63  per  cent  of  the  wood  was 
healthy  and  37  per  cent  diseased.  On  the  sprayed  trees  the  total 
length  of  new  shoots  measured  on  1891  growth  or  older  was  17,015 
inches;  of  this,  16,988  inches  was  of  healthy  wood  and  only  17  inches 
of  diseased  wood,  or  991  per  cent  was  healthy  and  i  per  cent  diseased.^ 
Man}^  peach  orchards- are  cultivated  under  conditions  of  moisture  and 
nourishment  that  enable  the  trees  to  grow  throughout  the  entire  sum- 
mer. In  such  situations  trees  badly  diseased  in  the  spring  are  apt  to 
so  far  recover  l^f  ore  frost  that  there  is  little  apparent  difference  between 
them  and  the  trees  saved  from  curl  by  the  use  of  sprays.  That  this 
recovery  is  not  entire,  however,  is  shown  by  actual  comparisons.  In  the 
Riviera  orchard.  Live  Oak,  Cal. ,  were  obtained  the  following  records,  in 
February,  1894,  f  ron  10  sprayed  and  10  unsprayed  Crawf  ords  Late  peach 
trees.     The  trees  are  fully  described  under  the  following  heading  of  this 

^  These  comparative  records  of  the  length  of  healthy  and  diseased  1)ranches  upon 
sprayed  and  unsprayed  trees  fully  serve  the  purpose  of  comparison  for  which  they 
are  here  intended.  There  is  another  phase  of  the  matter,  however,  which  should 
not  be  overlooked  or  misunderstood  at  this  time.  A  branch  classed  as  diseased  does 
not  mean  that  it  was  diseased  or  swollen  throughout  its  entire  length,  but  that 
external  signs  of  a  diseased  or  injured  condition  were  noted  at  some  point  in  its 
course.  If  it  be  supposed  that  one-third  of  the  injuries  noted  were  dead  ends  or 
other  imperfections  not  due  to  the  infecting  of  the  branch  by  the  fungus,  but  indi- 
rect injuries  arising  from  the  loss  of  foliage,  there  remain  two-thirds  of  the  injuries 
which  may  l)e  properly  assumed  to  be  due  to  the  infection  of  l)ranches  by  means  of 
mycelium  coming  from  diseased  leaves.  There  would  then  api)ear  to  l^e  25  per  cent 
of  tiie  cases  which  might  be  classed  as  diseased  from  mycelium  infection.  As  already 
indicated,  however,  this  does  not  mean  that  these  l)ranches  are  infected  throughout 
their  entire  length,  Init  show  one  or  more  points  of  infection  at  the  buds.  It  is 
thought  by  the  writer  that  not  more  than  1  bud  in  10  is  actually  infected  in  these 
diseased  branches.  If  this  estimate  is  approximately  correct,  the  number  of  infected 
buds  on  the  unsprayed  trees  would  be  represented  by  one-tenth  of  25  per  cent,  or  2.5 
per  cent  of  the  buds  on  the  tree.  In  brief,  it  is  believed  that  it  is  rare  for  more  than 
3  per  cent  of  the  buds  of  a  badly  disea.>^ed  tree  to  become  infected  by  the  mycelium 
from  diseased  leaves — in  other  wonls,  that  rarely  more  than  this  jjercentage  of  buds 
of  one  year  carry  a  perennial  mycelium  to  the  next  spring. 


94 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


chapter,  and  it  will  here  be  sufficient  to  state  that  the  growth  on  the 
sprayed  and  unsprayed  trees  could  be  fairly  compared.  The  sprayed 
trees  were  treated  with  the  sulphur,  lime,  and  salt  spraj"  in  the  winter  of 
1892-93.  Leaf  curl  developed  seriously  in  the  orchard  in  the  spring  of 
1893.  The  sprayed  trees  saved  their  foliage  and  bore  a  full  crop  of  fruit 
in  1893,  while  the  unsprayed  trees,  everywhere  surrounding  those  that 
were  sprayed,  lost  the  spring  foliage  and  most  of  the  fruit.  All  trees 
stood  upon  moist,  deep,  rich  river  bottom  land,  where  growth  could 
continue  throughout  the  season.  In  the  fall  of  1893  the  unspraj^ed 
trees  had  apparently  largely  overtaken  the  sprayed  trees  in  growth,  as 
the  former  had  carried  little  crop,  while  those  that  were  sprayed  had 
matured  a  full  crop.  That  the  unsprayed  trees  were  not,  however, 
fully  abreast  of  the  sprayed  trees  when  growth  ceased  in  1893,  is 
shown  by  the  measurements  recorded  in  February,  1891:  (table  11). 
These  measurements  were  made  on  various  sides  of  each  tree,  and  on 
lower  and  upper  limbs,  and  as  a  week  was  devoted  to  the  work,  the 
measurements  are  believed  to  bo  sufficiently  extensive  to  give  reliable 
results. 

Table  10. — Gain  in  number  of  lateral  shoots  and  spurs  Jruin.  old  vjood  on  sprayed  trees. 


Records. 

Trees. 

Sprayed. 

Unsprayed. 

Length  of  old  wood,  measured  in  inches,  on  sprayed  and  unsprayed  trees — 
Number  of  lateral  shoots  and  spurs  that  pushed  from  old  wood  in  1893 

8,255 

2,922 

0. 3539 

13 

7,363 
2,300 
0. 3124 

Gain  in  favor  of  sprayed  trees per  cent. . 

The  above  table  shows  that  13  per  cent  more  buds  had  pushed  into 
shoots  and  spurs  on  the  spra^^ed  trees,  in  the  summer  of  1893,  than  on 
the  unsprayed  trees.     All  represented  new  growth  from  old  wood. 

The  following  table  shows  that  the  length  of  the  new  growth  for  the 
entire  season  of  1893  on  the  sprayed  trees  was  6.4  per  cent  more  than 
that  produced  on  the  unsprayed  trees.  This  was  in  spite  of  the  facts 
that  the  unsprayed  trees  were  so  situated  that  growth  could  continue 
until  frost  and  that  they  had  not  carried  a  crop  of  fruit  as  had  the 
sprayed  trees: 

Table  1L — Gain  in  length  ofiww  growth  in  favor  of  sprayed  trees. 


Records. 

Trees.    • 

Sprayed. 

Unsprayed. 

Length  of  old  wood,  measured  in  inches,  on  sprayed  and  unsprayed  trees — 

8, 255 

7,363 

18, 174 
2,692 

16,390 

1,100 

20,866  1            17.490 

Inches  of  new  growth  per  inch  of  old  wood 

Gain  in  new  growth  in  favor  of  sprayed  trees per  cent. 


2.527 
6.4 


COMPARATIVE    DEVELOPMENT    OF    FRUIT    BUDS    AND    SPURS,       95 

The  nuinbiM-  of  leaf  buds  })roduc'ecl  on  the  spniyed  and  iinsprayed 
trees  per  lineal  inch  or  foot  of  old  wood  did  not  greatlj'^  diifer.  There 
was,  however,  a  gain  of  1  per  cent  in  favor  of  the  sprayed  trees,  as 
shown  below: 

Table  12. — (t'o(»,  in  number  of  leaf  buds  iv  furor  of  sprayed  IreeSy/^""'^ 


Rofords. 


Length  of  old  wood,  measured  in  inches,  on  sprayed  and  iinsprayed  trees. . 

Number  of  leaf  buds 

Average  number  of  leaf  buds  to  inch  of  wood 

Gain  in  favor  of  sprayed  trees per  cent 


The  tendency  of  the  new  growth  to  send  out  lateral  branches  and 
spurs  was  much  more  marked  upon  the  sprayed  than  upon  the 
unsprayed  trees,  the  gain  in  this  case  being  101)  per  cent.  This  is  a 
decided  advantage,  for  the  tree  is  thus  enabled  to  bear  a  heavier  and 
more  equall}'  distributed  crop  than  where  such  laterals  are  few. 

Tablk  13. — Gam    ia  number  of  lateral  xlioots  and  up itrs  front  new  wood  on  sprayed  trees. 


Records. 

Trees. 

Sprayed. 

Unsprayed. 

Length  of  new  wood,  measured  in  inches,  on  sprayed  and  unsprayed  trees... 
Number  of  lateral  shoots  and  spurs  froni  new  wood 

18, 174 
&40 

0.0a52 
109 

16,390 

276 

0.0168 

Gain  in  favor  of  spraved  trees per  cent. . 

A  complete  tabular  presentation  of  the  data  from  which  the  four 
preceding  tables  have  been  drawn  will  be  found  under  the  following 
heading. 


THE    DEVELOPMENT    OF    NEW    FRUIT    BUDS    AND   FRUIT   SPURS    FOR    THE 
YEAR    FOLLOW'INCx    AN    ATTACK    OF   CURL. 

In  February,  ISD-l,  while  the  action  of  the  sulphur  sprays  was  being 
considered  in  the  Riviera  orchard,  the  question  arose  as  to  the  rela- 
tive abilit}"  of  sprayed  and  unsprayed  trees  to  produce  fruit  buds  and 
fruit  spurs  for  the  year  following  a  severe  attack  of  curl.  Many  trees 
in  this  orchard  had  been  spraved  with  the  sulphur  sprat's  in  the 
winter  of  1892-93  for  the  d(^st ruction  of  the  San  Jose  scale  [Asjndio- 
tua jperniciosU'^.  The  manner  in  which  this  work  was  done  furnished 
an  excellent  opportunity  to  ascertain  the  facts  desired  respecting  the 
development  of  fruit  l)uds.  It  was  noted  during  the  early  part  of  the 
winter  that  individual  trees,  scattered  through  a  40-acre  block  of  4-year- 
old  Crawfords  Late,  had  become  infested  with  San  Jose  scale.  A 
careful  examination  of  this  part  of  the  orchard  was  then  made,  and 
each  tree  found  to  be  infested  with  the  scale  was  marked  for  spraying. 


96     PEACH  LEAF  CURL!  ITS  NATURE  AND  TREATMENT. 

Later  in  the  winter  Mr.  A.  D.  Cutts,  one  of  the  proprietors  and  the 
superintendent  of  the  orchard,  had  these  marked  trees  thoroughly 
sprayed  with  sulphur,  lime,  and  salt,  the  formula  used  being  as  fol- 
lows: Sulphur  15  pounds,  lime  30  pounds,  salt  10  pounds,  water  60 
gallons. 

While  this  spray  was  known  to  be  effective  against  San  Jose  scale, 
it  also  proved  very  effective  against  curl,  which  developed  seriously 
in  the  orchard  in  the  spring  of  1893.  The  result  of  the  spraying  was 
to  produce  a  most  striking  effect.  When  the  disease  developed,  the 
unspraj^ed  trees,  which  i-epresented  the  major  portion  of  this  40-acre 
orchard,  were  almost  wholly  denuded  of  foliage  and  largely  of  fruit, 
while  the  spraved  trees,  scattered  through  the  block,  were  in  full  foliage 
and  fruit.  This  orchard  was  selected  as  a  very  suitable  place  in  which 
to  study  the  relative  thrift  and  number  of  fruit  ])uds  and  spurs  pro- 
duced on  sprayed  and  unsprayed  trees  for  the  year  following,  and  for 
this  purpose  20  trees  were  selected  from  this  block  in  February,  189-1. 
Ten  of  these  trees  had  been  spra3'ed  in  the  winter  of  1892-93,  and  had 
thus  escaped  serious  injury  from  curl  in  the  spring  of  1893,  while  10 
of  them  had  not  been  sprayed  and  had  suffered  considerably  from  the 
disease.  These  20  trees  were  all  Crawfords  Late,  6  years  old  in  the 
winter  of  1893-91,  and  similar  in  other  respects,  the  soil,  situation, 
etc.,  being  the  sariie. 

The  work  of  counting  and  grading  buds  upon  these  sprayed  and 
unsprayed  trees  was  begun  about  the  middle  of  February,  1894,  and 
continued  for  a  week,  an  equal  amount  of  time  being  given  to  each  tree. 
To  make  all  records  as  representative  as  possible  of  all  portions  of  the 
trees  studied,  the  limbs  were  measured  and  the  buds  counted  and  classi- 
ffcd  upon  different  sides  of  each  tree  and  upon  both  lower  and  upper 
limbs.  In  the  selection  and  measurement  of  limbs,  as  well  as  in  the 
counting  and  classification  of  the  buds,  an  effort  was  made  to  correctly 
represent  the  conditions  existing  in  all  parts  of  each  tree,  and  of  all 
trees  alike.  After  the  selection  of  a  limb  for  study,  all  wood  grown 
prior  to  1893  was  measured  and  the  length  recorded.  Following  this 
all  the  shoots  and  spurs  of  1893  growth,  and  arising  from  the  old 
wood  measured,  were  counted  and  the  number  set  down.  All  these 
new  shoots,  with  the  exception  of  fruit  spurs  4  inches  or  less  in  length, 
were  then  measured.  Records  were  kept  of  the  length  of  the  new 
shoots,  the  number  of  well-developed  fruit  buds,  the  number  of  poorly 
developed  fruit  buds,  and  the  nimiber  of  leaf  buds  they  bore.  A 
record  of  the  number  of  lateral  shoots  and  fruit  spurs  from  the  growth 
of  1893  was  also  preserved.  The  results  of  this  work  are  brought 
together  in  the  two  tables  which  follow: 


DESCRIPTION  OF  PLATE  XXX. 

Views  of  the  right  and  left  sides  of  the  Gunnis  power  sprayer  of  San  Diego,  Cal. 
Tliis  sjirayer  is  one  of  the  liglitest,  most  compact,  and  most  practical  power  sprayers 
in  use  for  general  orchard  work.  It  supplies  2  or  4  lines  of  hose,  as  may  be  desired. 
A  tender  is  commonly  used  to  carry  the  spraying  materials  to  the  orchard,  where  an 
extra  rotary  pump,  worked  by  the  same  power  as  the  spray  pump,  rapidly  transfers 
the  spray  to  tlie  tank  of  the  spray  wagon.  Such  an  outfit  is  adapted  to  extensive 
orchard  work.  Mr.  II.  R.  Gunnis,  San  Diego,  Cal.,  is  the  ownerand  operator  of  this 
machine. 


Bull.  20,  Div.  Veg.  Phys.  8c  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XXX. 


Right  and  Left  Views  of  Power  Sprayer,  San  Diego,  Cal. 


COMPARATIVE    DEVELOPMENT    OF    FRUIT    BUDS    AND    SPURS.       *J7 


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19093— No.  20- 


98 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


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COMPARATIVE    DEVELOPMENT    OK    FRUIT    BUDS    AND    SPURS.       99 

In  the  preceding  tables,  the  number  of  shoots  and  spins  of  1893, 
which  arose  from  wood  of  189:2  or  earlier  (old  wood),  as  well  as  the 
length  of  the  old  wood  itself,  are  classed  under  the  general  head  of 
new  growth  from  old  wood.  The  measurements  of  the  growth  of 
1893,  and  the  number  of  lateral  shoots  and  fruit  spurs,  as  well  as  the 
number  of  fruit  and  leaf  buds  the  new  growth  produced,  are  classed 
under  the  head  of  new  wood.  The  buds  were  counted  in  a  uniform 
manner  upon  all  growth  measured,  except  the  buds  borne  by  fruit 
spurs,  w^hicli  are  estimated  at  3  buds  per  spur  in  the  tal)ulated  calcula- 
tions which  follow.  The  fruit  buds  have  been  divided  into  two  classes — 
well  developed  and  poorly  developed. 

In  considering  the  information  given  in  the  preceding  tables,  only 
those  facts  having  a  direct  bearing  on  the  fruit  buds  of  the  sprayed 
and  unsprayed  trees  will  be  taken  up  under  this  heading.  Those 
relating  to  length  of  new  growth,  number  of  new  shoots,  and  number 
of  leaf  buds  have  already  been  considered  under  the  preceding  head- 
ing of  this  chapter. 

The  following  digest  from  the  general  tables  shows  that  23,879  fruit 
buds  of  all  kinds  were  produced  by  the  new  growth  arising  from  8,255 
linear  inches  of  old  wood  on  10  sprayed  trees  in  1893 — an  average  of 
2.892  buds  per  inch  of  old  wood.  The  average  number  of  buds  per 
inch  of  old  wood  on  the  10  unsprayed  trees,  obtained  in  a  similar  man- 
ner, was  2.686.  These  figures  show  that  the  sprayed  trees  produced 
7f  per  cent  more  fruit  buds  of  all  kinds  in  the  summer  of  1893  than 
were  produced  by  the  unsprayed  trees.  These  were  fruit  buds  for 
the  crop  of  1894,  and  upon  trees  bearing  a  full  crop  in  1893,  while  the 
contrasted  unsprayed  trees  bore  very  little. 

Table  16. — Gain  in  total  number  of  fruit  buds  on  sprayed  trees. 


Trees. 


Records. 


Length  of  old  wood,  measured  in  inches,  on  sprayed  and  unsprayed  trees . 

TotaJ  number  of  fruit  buds  of  all  kinds 

Average  number  of  same  to  inch 

Gain  in  favor  of  sprayed  trees j.per  cent.. 

The  percentage  of  gain  in  the  gross  number  of  fruit  buds  shown  by 
the  spra3'ed  trees  is  considerable,  but  it  represents  only  partially  the 
advantages  derived  from  the  spray.  P^xaminations  of  the  unsprayed 
trees  showed  that  a  large  percentage  of  the  fruit  buds  they  had  pro- 
duced in  1893  were  imperfect,  many  of  them  being  so  poorly  developed 
that  fruit  could  not  be  expected  from  them.  The  following  table  shows 
the  average  number  of  imperfectly  developed  fruit  buds  on  the  spra3''ed 
trees  to  be  0.944  per  linear  inch  of  old  wood,  while  on  the  unsprayed 
trees  the  average  jxt  inch  of  old  wood  was  1.24l>.  This  shows  32  per 
cent  more  imperfect  fruit  buds  on  the  unsprayed  than  upon  the  sprayed 
trees  at  the  close  of  the  growing  season  of  1893. 


100 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


Table  17. — Excess  of  imperfectly  developed  fruit  buds  on  unsprayed  trees. 


Records. 

Trees. 

Sprayed. 

Unsprayed. 

Length  of  old  wood,  measured  in  inches,  on  sprayed  and  unsprayed  trees 

8,255 
7,792 
0.944 

7,363 

9,200 

1.249 

32 

Average  number  of  imperfectly  developed  fruit  buds  to  inch  of  wood 

In  comparing  the  number  of  well-developed  fruit  buds  which  were 
produced  in  ls'.);5  by  the  sprsiyed  and  un.spraycd  troos.  independent  of 
the  number  of  spur  l)uds,  it  was  learned  that  the  number  upon  the 
spra3'ed_ti::£es^was  20  per  cent  greater,  as  shown  in  the  following  table, 
than  the  nuraber  produced  by  the  unspraj^ed  trees. 

Table   18.^ — Gain  in    icell-develojied    fruit   buds,    exclusive    of  spars,  on  sprayed  over 

unsprayed  trees. 


Records. 

Trees. 

Sprayed.    Unsprayed. 

Length  of  old  wood,  measured  in  inches,  on  sprayed  and  unsprayed  trees 

8,255               7,363 

12,049                8,927 

1. 459                1. 212 

Gain  in  favor  of  sprayed  trees per  cent. . 

20    

Taking  the  aggregate  of  all  well-developed  fruit  buds,  including  the 
spurs,  at  an  average  of  3  buds  each,  the  sprayed  trees  make  a  still  better 
showing  when  contrasted  with  the  unsprayed.  The  average  number  of 
all  well-developed  buds  on  the  sprayed  trees  was  1.949  per  linear  inch 
of  old  wood,  and  on  the  unsprayed  trees  1.437  per  inch  of  old  wood. 
This  shows  a  gain  of  35  per  cent  in  well-developed  fruit  buds  in  favor 
of  the  sprayed  trees.     These  facts  are  shown  in  tabular  form  as  follows: 

Table  19. — Gain  in  spur  buds  and  other  well-developed  fruit  buds  on  sprayed  over 

wisprayed  trees. 


Records. 


Length  of  old  wood,  measured  in  inches,  on  sprayed  and  unsprayed  trees 

Aggregate  of  spur  buds  and  of  other  well-developed  fruit  buds 

Average  number  of  same  to  inch 

Gain  in  favor  of  sprayed  trees per  cent. . 


One  of  the  most  striking  contrasts  shown  by  the  data  obtained  in 
these  field  studies  is  that  existing  between  the  number  of  fruit  spurs 
and  spur  buds  produced  b}^  the  sprayed  and  unsprayed  trees  in  1893. 
There  was  a  net  gain  in  the  number  of  fruit  spurs  and  spur  buds  on 
the  sprayed  trees  of  118  per  cent  above  the  number  produced  b}^  the 
unsprayed  trees,  a  fact  that  should  certainly  appeal  directl}^  to  the 
business  faculties  of  every  grower  of  peaches.  It  should  also  be 
remembered  that  these  sprayed  trees  had  carried  a  crop  while  pro- 


COMPAEATIVE    DEVELOPMENT    OF    FRUIT    BUDS    AND    SPURS.     101 


ducing  these  fruit  spurs  for  the  following  year,  while  the  unsprayed 
trees  had  borne  but  few  peaches.  The  facts  here  discussed  are  shown 
in  the  table  that  follows. 

Tahle  20. — Gain  in  number  of  spur  buds  on  sprayed  over  unsprayed  trees. 


Trees. 


Rofords. 


Lengtli  of  old  wood,  measured  in  inches,  on  sprayed  and  unsprayed  trees 

Total  number  of  spurs 

NumbiT  of  spur  buds,  estimated  at  3  buds  per  spur 

Average  number  of  spurs  per  inch 

Average  number  of  spur  buds  per  inch 

Gain  in  favor  of  sprayed  trees per  cent. . 


Besides  comparing  the  number  of  fruit  buds  produced  in  1893  by 
the  sprayed  and  unsprayed  trees,  it  is  desirable  to  contrast  the  bud- 
producing  abilities  of  the  upper  and  lower  portions  of  these  trees. 
It  is  generally  conceded  as  desirable  that  the  crop  of  a  peach  tree  should 
be  borne  as  largely  as  possible  upon  the  lower  limbs,  and  anything 
tending  to  this  result  may  prove  of  value.  Peach  leaf  curl,  being  due 
to  a  fungous  parasite,  has  a  tendency  to  do  more  injury  to  the  lower 
than  to  the  upper  portions  of  the  trees  affected.  The  atmospheric  con- 
ditions are  more  favorable  for  the  germination  of  spores  and  to  fungous 
growth  in  the  lower  and  more  shaded  portions  of  the  tree,  and  the 
lower  branches  accumulate  greater  numbers  of  fungous  spores  than  the 
upper  branches.  In  the  following  table  it  is  shown  that  the  total  number 
of  fruit  buds  produced  b}^  the  lower  limbs  of  the  sprayed  trees  was  7 
per  cent  greater  than  the  number  produced  by  the  upper  limbs,  com- 
paring equal  lengths  of  new  wood  in  each  case.  On  the  unsprayed 
trees,  however,  the  upper  limbs  produced  5  per  cent  more  fruit  buds 
per  linear  unit  of  new  wood  than  the  lower  limbs.  This  shows  a 
difference  of  12  per  cent  in  favor  of  the  sprayed  trees.  The  tabulated 
figures  are  as  follows: 

Tablk  21. — -Gain  in  total  number  of  fruit  buds  on  lower  limbs  of  sprayed  trees  over  those 
of  unsprayed  trees,  as  compared  with  upper  limbs  of  each,  respectively. 


Records. 

Trees. 

Sprayed. 

Un.sprayed. 

Length-  of  new  wood,  measured  in  inches,  on  upper  limbs 

10,964 
1,358 

9,770 

Length  of  spurs,  estimated  at  2  inches  per  spur  .   . 

554 

Total  length  of  new  wood  on  upper  limbs 

12, 322 

10,324 

7,210 
1,334 

6  6''0 

Length  of  spurs,  estimated  at  2  inches  per  spur 

546 

Total  length  of  new  wood  on  lower  limbs 

8,544 

7,166 

Total  number  of  fruit  buds  on  upper  limbs 

13, 724 
10, 155 
1.114 
1.189 
7 

11,901 

7,876 

1  1.53 

1.099 

Gain  in  favor  of  lower  linilis  on  sjirityed  trees per  cent.. 

5 

Difference  in  favor  of  sprayed  trees '. do 

12 

102 


PEACH    LEAF    CURL:    ITS    NATURE    ANr>    TREATMENT. 


By  contrasting  only  the  well-developed  and  spur  fruit  buds  it  is 
learned  that  there  was  14  per  cent  in  the  number  of  buds  in  favor  of 
the  lower  limbs  on  the  sprayed  trees  and  4  per  cent  in  favor  of  the 
upper  limbs  on  the  unsprayed  trees.  This  showed  a  difference  of  18 
per  cent  in  favor  of  the  lower  limbs  of  the  sprayed  trees.  The  entire 
comparison  is  given  in  the  table  which  follows: 

Table  22. — Gain  in  number  of  well-developed  and  spur  fruit  buds  on  the  lover  limbs  of 
sprayed  over  unsprayed  trees,  as  compared  with  upper  limbs  of  each,  respectively. 


Records. 

Trees. 

Sprayed. 

Unsprayed. 

10,964 
1,358 

9,770 

554 

Total  length  of  new  wood  on  upper  limbs 

12, 322 

10,324 

Length  of  new  wood,  measured  in  inches,  on  lower  limbs  . 
Length  of  spurs,  estimated  at  2  inches  per  spur 


Total  length  of  new  wood  on  lower  limbs . 


7,210 
1,334 


8,544 


Number  of  well-developed  and  spur  fruit  buds  on  upper  limbs 

Number  of  same  on  lower  limbs 

Average  number  of  same  per  inch  on  upper  limbs 

Average  number  of  same  per  inch  on  lower  limbs 

Gain  in  favor  of  lower  limljs  <in  s|irayed  trees per  cent. 

Gain  in  favor  of  upper  limbs  on  unsprayed  trees do. . . 

Difference  ir  favor  of  sprayed  trees do. . . 


8,975 
7, 112 
0.728 
0.832 
14 


6,620 
546 


7,166 


6,340 
4, 237 
0.614 
0.591 


CHAFrER  Vl. 

INFLUENCE  OF  SPRAYS  ON  THE  FRUITING  OF  THE  TREES. 
THINNING    THE    FRUIT   OF    SPRAYED   TREES. 

The  general  discussion  of  the  spray  work  conducted  in  the  Rio  Bonito 
orchard  will  be  found  in  Chapter  IV,  and  it  is  therefore  not  necessary 
to  review  thc^se  matters  here.  As  soon  as  growth  was  well  started 
in  this  orchard  in  the  spring  of  1895,  it  became  evident  that  the  fruit 
would  have  to  be  thinned  on  a  portion  of  the  Lovell  trees  comprising 
the  experiment  block.  The  peaches  were  setting  thickly  on  both 
sprayed  and  uusprayed  trees,  but  as  leaf  curl  developed,  the  young 
fruit  upon  the  control  trees  began  to  fall,  while  that  upon  the  sprayed 
trees  remained  firmly  attached  and  grew  rapidly. 

When  the  3"oung  peaches  had  reached  the  size  of  hickorj"  nuts,  and 
the  pits  were  forming,  the  danger  of  dropping  from  curl  had  passed, 
and  the  thinning  of  fruit  on  overloaded  trees  was  then  undertaken. 
To  enable  the  writer  to  make  just  comparisons  of  the  merits  of  the 
various  sprays  in  saving  fruit,  it  became  necessarj^  to  carefull}'  record 
the  amount  and  number  of  peaches  thinned  from  all  trees  in  the  experi- 
ment block.  Thinning  fruit  is  an  equalizing  process,  and  to  equalize 
the  crop  upon  spraj^ed  and  unsprayed  trees  or  upon  trees  treated  with 
different  sprays,  would  be  to  destroy  the  contrast  in  the  amount  of 
fruit  arising  from  the  use  of  different  formuhe.  This  would  result  in 
the  loss  of  the  very  facts  which  it  was  hoped  to  obtain  from  the  experi- 
ments, unless  records  of  the  fruit  thinned  off  were  preserved.  For 
the  preservation  of  such  records  the  following  plan  was  adopted: 
Canvas  sheets  of  large  size,  commonly  used  in  the  harvest  of  the  almond 
crop  in  the  same  orchard,  were  spread  beneath  the  trees  to  be  thinned. 
The  3'oung  peaches  were  allowed  to  fall  upon  the  canvas  as  picked,  and 
the  canvas  was  moved  as  necessary.  The  fruit  thus  thinned  was 
poured  from  the  canvas  into  picking  boxes  beneath  the  tree  from  which 
it  was  thinned.  By  this  plan  the  fruit  thinned  from  each  tree  was 
kept  by  itself.  After  an  experiment  row  of  10  trees  had  been  thinned, 
the  fruit  picked  from  each  tree  was  separately  weighed  and  the  weight 
recorded.  From  3  trees  of  the  row  sufficient  fruit  was  now  taken  to 
amount  to  25  pounds.  The  peaches  in  this  25  pounds  were  then 
counted,  the  number  entered  with  the  other  re'cords  of  the  row,  and 
on  this  basis  the  average  number  of  small  peaches  per  pound  for  the 
row  was  determined.  By  multiplying  the  number  of  pounds  of  young 
peaches  thinned  from  each  tree  by  the  average  number  of  peaches 
per  pound,  as  above  obtained,  the  writer  was  able  to  determine  quite 
accuratel}^  the  number  of  peaches  thinned  from  each  tree  of  the  row. 

103 


104 


PEACH    LEAF    CUKL*.    ITS    NATURE    AND    TREATMENT. 


When  the  work  on  one  experiment  row  was  completed,  the  fruit  from 
a  second  row  of  10  trees  was  gathered,  weighed,  and  counted  in  like 
manner,  and  this  process  was  followed  for  each  row  of  the  block  which 
required  thinning. 

From  the  field  records  thus  gathered  two  tables  have  been  carefully 
compiled,  the  first  showing  the  actual  weight  of  young  peaches  picked 
from  each  tree  thinned  in  the  block,  and  the  second  the  computed 
number  of  peaches  which  these  weights  represent,  as  determined  by 
the  above-described  method. 

Table  23. —  Weight  of  peaches  ihinned  from  the  sprayed  Lovell  peach  trees  in  the  experi- 
ment block  of  the  Rio  Bonito  orchard  in  the  spring  of  1895.  (a) 


Row  No. 

Actual  weight   in   pounds   of  thinned 
peaches  from  trees  Nos.  — 

Total 

weight  of 

peaches 

in  row. 

Number 

of 
peaches 

in  25 
pounds. 

Average 
number 

of 
peaches 

per 
pound. 

Total 

number 

of 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

peaches 
per  row. 

1 

15 

16i 

18 

33 

20i 

22i 

27 

45 

50 

35 

Pounds. 
282i 

4S2 

19.28 

5,442 

2 

3             

27 

22 

15 

20 

22i 

21 

30i 

16i 

29 

16 

219i 

550 

22.00 

4,829 

4 

5 

6    

18 
17 

2 
25 

15 
11 

6 

7i 

15 
12 

3 
9^ 

2U 
15 

5 
6 

19 
5i 

l&k 

8i 

121 
117 

486 
484 

19.44 
19.36 

2,352 

7 

8 

2,265 

9              

36 
30 

21 
30i 

15 
24 

131 
10 

18i 
17 

25 
25 

36 
40 

6i 
19i 

6 

17 

7i 
20i 

185 
2334 

522 
466 

20.88 
18.64 

3,863 

10 

11 

4,352 

12             

31 
23i 

13 
14i 

3 
2 

10 
2k 

6 

18 

16^ 
13i 

;i 

19i 
2^ 

lOi 
3i 

5i 

133i 
93 

511 
495 

20.44 
19.80 

2,729 

13 

1,841 

14 

15.           '. . 

82 
20i 

44 
6 

27 
15 

31 
3i 

24 
9i 

40 
5 

45 
17 

23 
17i 

29i 
14 

22 
13 

367i 
121 

528 
496 

21. 12 
19.84 

7,762 

16 

2,401 

17 

18 

32 
24 

17 
35 

26 
29 

16 
16 

17 
25 

8 
14 

10 
13 

6 
11 

14 

7 

4 
12 

150 
186 

504 

486 

20.16 
19.44 

3,024 

19 

3,616 

20 

21 

68 
33 

48 
51 

26 
35 

28 
21 

48^ 
35 

49 

58 

58 
41 

21 
22 

29i 
29 

61i 
60 

437i 
385 

484 
472 

19.36 

18.88 

»,470 

22 

7,269 

23 

24 .          

25 

42 

20 

22 

18 

28 

21 

37 

38 

43 

51 

320 

449 

17.96 

5,747 

26 

27 

34 

18 

34 
21 

35 
32 

11 
29 

14 
31 

35 
33 

30 
34 

22 
30 

21 

63 

23 
50 

259 
341 

495 
421 

19.80 
16.84 

5,128 

28 

5, 742 

29 

30 

55 

49 

42 

43 

60 

43 

41 

35 

70 

86 

524 

487 

19.48 

io, 208 

31 

32 

31 

47 

15 
51 

18 
34 

20 
40 

22 
22 

18 
39 

27 
33 

8 
29 

159 
381 

514 

483 

20.56 
19.32 

3,269 

33 

39 

47 

7,361 

34  ... 

35 

36  . 

62 
23 

63 
35 

23 
14 

'16' 

57 
11 

42 
31 

46 
26 

57 
31 

54 

28 

62 
46 

466 
255 

522 
480 

20.88 
19.20 

9,730 
4,896 

37 

38 

15 
40 

6 
26 

6 
39 

8 

10 

22 
37 

26 
34 

17 
29 

15 
34 

25 
27 

150 
266 

553 

547 

22.12 
21.88 

3,318 

39 

5,820 

40 

41 

54 

52 

27 

24 

26 

12 

27 

8 

35 

28 

293 

508 

20.32 

5,953 

43 

44 

6 
25 

8 
23 

11 
21 

5 
11 

6 
22 

36 
196 

537 
504 

21.48 
20.16 

773 

45 

46 

17 

20 

16 

27 

14 

3,951 

47  .          ... 

48 

7 

6 

3 

5 

8 

4 

33 

511 

20.44 

675 

49 

50 

51 

15 

22 

8 

12 

11 

12 

12 

13 

18 

17 

140 

533 

21.32 

^2,985 

52 

53 

54 

30 

34 

44 

18 

17 

27 

30 

2t 

36 

17 

274 

508 

20.32 

5,568 

55 

56 

22 
21 

40 
35 

44 
16 

18 
20 

17 
11 

27 
19 

30 
20 

21 
29 

36 
32 

17 
37 

272 
240 

520 
547 

20.80 
21.88 

5,658 

57 

5,251 

58 



a  For  plat  of  orchard  see  p.  69;  for  sprays  applied  see  p.  73. 


THINNING    THE    FRUIT    OF    SPRAYED    TREES. 


106 


By  referring  to  the*  above  table  it  will  be  seen  that  only  those  rows 
which  were  spraj^ed  in  the  spring  of  1895  were  thinned,  and  that  a 
portion  of  these  required  but  little  thinning.  The  reasons  for  this  lie 
in  the  severe  action  of  the  disease  upon  the  unsprayed  rows  and  those 
sprayed  with  weak  or  luisatisfactory  spra3\s,  in  which  cases  the  fruit 
fell  from  disease.  The  table  shows  the  weight  of  thinned  peaches  per 
tree,  the  total  weight  of  peaches  thinned  from  the  row,  the  number 
of  peaches  contained  in  25  pounds,  the  average  number  of  peaches  per 
pound,  and  the  total  numl)er  of  peaches  thinned  from  the  row. 

In  the  table  which  follows  the  pounds  have  Ijeen  reduced  to  show 
the  number  of  peaches,  the  reduction  being  made  according  to  the 
method  already  described.  Comparison  of  the  total  number  of  peaches 
thinned  from  the  separate  rows,  as  given  in  the  two  tables,  will  show 
slight  variations  in  the  units  column  in  several  cases.  These  varia- 
tions arise  from  the  gain  or  loss  in  fractions  resulting  from  the  use 
of  the  different  methods  which  it  was  necessary  to  employ  in  obtain- 
ing the  figures  shown  in  the  two  tables. 


Table  24. — Xumber  of  peacltes  thinned  from  the  sprayed  Lovell  jyeadi  trees  in  the  experi- 
ment block  of  the  Rio  Bonito  orchard  in  the  spring  of  1895.  (a) 


Row 

Number  of  peaches 

thinned  from  sprayed  trees  Nos 

- 

Total 

No. 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

1 

289 

318 

347 

636 

390 

434 

521 

868 

964 

675 

5  442 

2 

3 

594 

484 

330 

440 

495 

462 

671 

363 

638 

352 

4,829 

4 

5 

6 

350 
329 

39 

484 

292 
213 

145 

292 
232 

58 
184 

418 
290 

97 
116 

369 
106 

321 
165 

2,353 
2,264 

7 

8 

9 

752 
559 

438 
569 

313 

447 

282 
186 

386 
317 

522 
466 

752 
746 

136 
363 

125 
317 

157 
382 

3,863 
4,352 

10 

11 

12 

634 
465 

266 

287 

61 
40 

204 
50 

123 
356 

337 
267 

31 

148 

399 
50 

215 
69 

460 
109 

2  730 

13 

1,842 

14 

15 

1,732 
407 

929 
119 

570 
298 

655 
69 

507 

188 

845 
99 

950 
337 

486 
347 

623 
278 

465 
258 

7,762 
2,400 

16 

17 

18 

645 
467 

343 
680 

524 
564 

323 
311 

343 

486 

161 
272 

202 
253 

121 
214 

282 
136 

81 
233 

3,025 
3,616 

19 

20 

21 

1,316 
623 

929 
963 

503 
661 

542 
396 

939 
661 

949 
1,095 

1,123 
774 

407 
415 

571 
548 

1,191 
1,133 

8,470 
7,269 

22 

23 

24 

25 

754 

359 

395 

323 

503 

377 

665 

(«2 

772 

916 

5,746 

26 

27 

673 
303 

673 
354 

693 
.  539 

218 
488 

277 
522 

693 
556 

591 
573 

436 
505 

416 
1,061 

455 
842 

5,128 
5,743 

28 

29 

30 

1,071 

955 

818 

838 

1,169 

838 

799 

682 

1,364 

1,675 

10, 209 

31 

32 

G37 
908 

308 
985 

370 
657 

411 
773 

452 
425 

370 
753 

555 
638 

1C)4 
560 



3,267 
7,360 

33 

753 

908 

34 

36 

1,295 
442 

1, 315 
672 

480 
269 

""i92' 

1,190 
211 

877 
595 

960 
499 

1,190 
595 

1,128 
538 

1,295 
883 

9,730 
4,8% 

36 

37 

38 

332 
875 

133 
569 

133 
853 

177 

221 

487 
810 

575 
744 

376 
635 

332 

744 

553 
591 

3,319 
5,821 

39 

40 

41 

1,097 

1,057 

549 

488 

528 

244 

549 

163 

711 

569 

5,955 

42 

a  For  plat  oi  orchard  see  p.  69;  for  sprays  applied  see  p.  73. 


106 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


Table  24. — Number  uf  peaches  thinned  from  the  sprayed  Lovell  peach  trees  in  the  experi- 
ment block  of  the  Eio  Bonito  orchard  in  the  spring  of  1895 — Continued. 


Row 

Number  of  peaches  thinned  from  sprayed  trees  Nos.— 

Total. 

No. 

1.     ■ 

2. 

3. 

4. 

5. 

6.             7. 

8. 

9. 

10. 

43 

44 

129 
504 

172 

464 

236 
423 

107 
222 

129 
444 

773 

45 

343 

403 

323 

544 

282 

3,952 

46 

47 

48 

143 

123 

61 

102 

164 

82 

675 

49 

50 

j 

51 

320 

469 

171 

256 

235 

256 

256 

277 

384 

362 

2,986 

52 

53 

54 

610 

691 

894 

366 

345 

549 

610 

427 

732 

345 

5,569 

55 

56 

458 
459 

832 
766 

915 
350 

374 
438 

354 
241 

562 
416 

624 
438 

437 
635 

749 
700 

354 
810 

5,669 

57 

5,253 

58 

1 

GATHERING   FRUIT    OF   SPRAYED   AND   UNSPRAYED    TREES. 

The  fruit  of  the  Lovell  variety  ripened  rapidly  iu  the  Sacramento 
Valley  after  the  middle  of  August,  1895.  On  the  experiment  trees  a 
large  portion  of  the  crop  was  sufficiently  matured  for  shipment  to  the 
canneries  by  the  20th  of  that  month.  By  that  date  the  plans  had 
been  made  for  the  gathering  of  the  crop,  which  work  was  completed 
before  the  1st  of  September.  The  fruit  was  gathered  at  two  pick- 
ings, the  second  picking  beginning  shortly  after  the  close  of  the  tirst. 
The  crop  was  marketed  in  three  ways: 

(1)  All  perfect  peaches  above  a  standard  size  adopted  by  the  can- 
neries, and  sufficiently  firm  to  bear  shipment  hy  rail  from  Biggs  to 
Oakland,  Cal. ,  a  distance  of  about  140  miles,  were  sold  to  a  firm  at 
the  latter  point  at  $30.80  per  ton,  f.  o.  b.  cars  at  Biggs.  This  fruit 
comprised  about  51:  per  cent  of  the  yield  of  the  experiment  block. 

(l2)  All  perfect  peaches  of  canning  size  which  were  too  mature  to 
bear  the  delay  and  long  shipment  b}"  rail  to  Oakland  were  shipped  to 
a  cannery  at  Chico,  Cal.,  a  distance  of  about  30  miles.  This  fruit 
brought  $30  per  ton,  f.  o.  b.  cars  at  Biggs.  It  comprised  about  30 
per  cent  of  the  yield  of  the  experiment  block. 

(3)  Such  fruit  as  was  below  cannery  size,  overmature,  or  imperfect 
in  any  respect  was  sent  to  the  drying  ground  to  be  dried.  In  the  cal- 
culations of  the  present  work  this  fruit  is  valued  at  three-fourths  of  a 
cent  per  pound  in  the  green  state.  This  is  less  than  the  equivalent  of 
dried  fruit  was  worth  at  the  time  of  curing  after  allowing  for  the  cost 
of  drying.  The  fruit  sent  to  the  diying  ground  represented  about  16 
per  cent  of  the  yield  of  the  experiment  block. 

The  work  of  gathering,  weighing,  and  grading  the  crop  of  the 
experiment  rows  was  carefully  systematized.  As  before  shown,  the 
experiment  block  was  20  trees  wide  from  east  to  west,  and  through 
the  center  from  north  to  south  a  driveway  was  made,  so  that  the  rows 


I.  20.  Div.  Veg    Phys.  &  Path.,  U.  S.  Dept    of  Agriculture. 


Plate  X. 


O    "H 


CD     - 


t-      t 

UJ      z 


o    —. 

CC.     Z 


H    ■= 


3      •— 
Q       - 

o     ■/• 


DESCRIPTION  OF  PLATE  X. 

Experiments  at  Biggs,  Cal.  (Bordeaux  mixture.)  Fruit  gathered  from  row  15  of 
the  experiment  block  of  the  Rio  Bonito  orchard  in  the  summer  of  1895.  The  formula 
for  the  spray  used  on  this  row  was  6  pounds  copper  sulphate,  15  pounds  quicklime, 
45  gallons  of  water.  The  10  trees  of  the  row  matured  4,351  pounds,of  fine  peaches, 
which  are  shown  in  the  picking  Ixixcs.  The  trees  of  the  adjoining  unsprayed  row. 
No.  14,  bore  only  928  pounds.  The  value  of  the  fruit  matured  on  row  15  a\;^  $H0.02i, 
on  "row  14  it  was  $13.24,  aTnet  gain  from  spraying  U'  trees  of  $46  after  alio  whig  .for — 
The  cost  of  spraying!  This  gain  resulted  after  more  than  one-third  of  the  peaches 
had  been  thiiiifed  from  the  sprayed  row,  while  none  had  been  thinned  from  row  14. 
The  total  number  of  peaches  set  by  the  trees  of  row  15  was  21,272,  by  those  of  row 

14  it  was  2,855.     The  comparative  average  net  gain  shown  by  the  spray  used  on  row 

15  was  619  per  cent. 


GATHKRINO    FRUTT    OF    SPRAYED    AND    UNSPRAYED    TREES.      107 

on  oither  side  wore  it)  trees  lon<^  from  east  to  west.  One  picker  was 
assigned  to  each  tree  of  the  row  across  the  block,  thus  making  ten 
pickers  on  each  side  of  th(>  driv'e,  or  twenty  in  all,  and  an  extra  man  was 
assigned  as  superintendent  of  the  twenty  pickers,  to  see  tliat  all  instruc- 
tions were  carefully  carried  out.  Every  man  was  instructed  to  leave 
all  fruit  h(^  pickinl  ])eneath  the  tree  from  which  it  was  gathered,  pick- 
ing boxes  having  been  previousl}^  distributed  for  this  purpose. 

The  work  of  picking  began  at  the  south  end  of  the  experiment 
block.  AYhen  the  fruit  which  was  sufficiently  matured  had  been 
gathered  and  placed  in  the  boxes  ])eneath  a  tree,  the  picker  proceeded 
to  the  next  tree  north,  thus  following  the  same  north-and-south  row 
until  he  had  passed  entirely  through  the  block,  and  when  each  man 
had  thus  completed  his  north-and-south  row  the  entire  block  had  been 
picked  over,  the  fruit  being  beneath  the  trees  from  which  it  came. 
The  first  and  second  pickings  were  conducted  in  this  manner,  but  the 
second  was  not  begun  until  after  the  first  was  completed  and  the 
gathered  fruit  had  been  removed  from  beneath  the  trees. 

The  process  of  collecting  the  fruit  of  the  first  picking  l)egan  as  soon 
as  the  pickers  had  completed  an  east-and-west  row  and  had  proceeded 
to  the  next  row  toward  the  north.  Four  men  were  employed  to  collect 
and  weigh  the  peaches — two  to  collect  the  fruit  in  the  orchard  and 
two  to  weigh,  count,  and  keep  the  records.  The  fruit  was  brought 
from  the  east  and  from  the  west  to  the  central  driveway  on  a  low  plat- 
form wagon  drawn  b}^  one  horse.  The  boxes  of  fruit  gathered  from 
the  10  trees  of  each  experiment  row  were  piled  at  the  side  of  the 
driveway,  close  to  the  last  tree  of  the  row.  The  boxes  of  fruit  from 
each  tree  were  also  distinguished  by  means  of  cards  bearing  the 
number  of  the  tree  from  under  which  the  boxes  were  taken  (PI.  X). 

The  weighing  began  as  soon  as  the  fruit  from  the  10  trees  of  an 
experiment  row  had  been  piled  at  the  side  of  the  central  drive.  Plat- 
form scales  were  placed  on  a  level  base  close  to  the  fruit  boxes,  and 
the  fruit  from  each  tree  of  the  row  was  weighed  separately.  The  gross 
weight  was  recorded  for  each  tree,  as  well  as  the  immber  of  picking 
boxes.  The  average  weight  of  the  picking  boxes  used  was  afterwards 
carefully  determined,  and  from  these  data  the  net  weight  of  fruit  was 
ascertained  and  tabulated  for  each  tree  of  each  row  of  the  block. 
After  the  weight  of  fruit  for  each  tree  of  an  experiment  row  was  thus 
learned,  100  pounds  of  peaches  were  weighed  out  from  tjqjical  boxes 
of  several  trees  of  the  row.  The  number  of  peaches  in  this  lOO  pounds 
of  fruit  was  then  ascertained  by  counting,  the  number  ))eing  recorded 
with  the  other  data  for  the  row.  The  fruit  of  all  the  experiment  rows 
was  weighed  and  the  average  size  of  the  peaches  determin(nl  ])y  count- 
ing, as  here  indicated. 

Following  close  after  the  weighers  came  five  or  six  sorters.  These 
men  graded  the  fruit,  according  to  the  requirements  already  outlined, 
into  three  classes — one  for  an  Oakland  canner}",  one  for  a  Chico  can- 
nerv,  and  a  third  class  for  drvinijf.     These  three  classes  constituted 


108 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


really  but  two  qualities  of  fruit — a  first  quality  for  canning,  and  a 
second  quality  for  drying.  After  the  fruit  of  a  row  was  graded  a 
careful  count  of  the  number  of  picking  boxes  of  each  class  of  fruit 
was  made,  and  the  numbers  recorded.  From  these  figures  were  deter- 
mined the  proportions  of  the  total  yield  of  the  row  which  belonged  to 
the  different  classes  of  fruit.  The  same  process  of  picking,  collecting, 
weighing,  counting,  grading,  and  recording  was  followed  for  the 
second  picking  as  for  the  first. 

In  the  following  table  are  shown  the  net  weights  of  fruit  gathered 
at  the  first  picking  from  each  tree  of  the  entire  block  of  58  experi- 
ment rows,  with  the  total  weight  for  each  row. 

Table  25. — Weight  of  peaches  of  first  incking  from  the  Lovell  trees  of  the  experiment 
block  of  the  Rio  Bonito  orchard,  gathered  in  the  fall  of  1895. 


Row  No. 

Weight  of  fruit,  in  pounds,  gathered  at  first 
picldng  from  trees  Nos. — 

Total  net 
weight 
of  fruit 
in  row. 

Number 
of  trees 
in  row. 

Average 
weight 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

per  tree. 

1 

75 
51 

164 
69 
42 

190 
88 
93 

259 

216 

109 
89 

121 
71 
74 
75 

267 
29 

271 

?75 

142 
122 
140 
129 

36 
193 
139 

22 
162 
332 

30 
111 
200 
114 
538 
303 

55 
322 
365 
110 
470 
539 

88 

65 
386 

71 
438 
573 

98 
237 
127 
132 
159 

94 
237 
129 

69 
140 
330 

65 
274 
128 
108 
246 
296 

64 
139 
137 

61 
214 
277 
126 

62 
449 

97 
314 
277 

99 

207 
137 
147 

31 

56 
175 
169 

11 
202 

89 

86 
191 

70 
109 
253 

87 

52 
242 
144 
109 
405 
267 

54 

48 
180 

16 
116 
298 

64 
258 
134 
252 
401 

53 

'iii' 

27 
166 

147 

54 
157 

57 

73 
228 
181 

39 
218 
219 

83 
304 
161 

47 
474 
298 

88 
341 
331 

32 
498 
544 

62 

43 
426 

19 
166 
400 

60 
323 
149 
315 
250 
107 
563 
188 
198 
273 

118 
111 
179 
120 
140 

97 
183 
151 
248 
240 
107 
154 
203 
114 
474 
216 
119 
233 
364 

27 
431 
556 

95 

52 
424 

62 
425 
489 

90 
219 
179 
218 
373 
148 
491 
354 

84 
234 
384 

49 
200 
145 

45 
164 
324 

56 
116 

79 

60 
120 
207 
■  84 

63 
421 
153 
181 
282 
195 

262 

90 
289 

87 
159 
212 
180 
115 
233 
249 
114 
247 
209 

91 
573 
451 

58 
296 
245 

32 
617 
469 

75 

48 
565 
109 
513 
489 

33 
296 
111 
209 
428 

79 
597 
365 
127 
284 
439 

53 
410 
223 

97 
139 
413 

42 
105 
182 

86 
118 
251 

25 

44 
392 
137 
244 
313 

83 

190 
140 
241 

74 
100 
212 
222 

39 
234 
297 

41 
168 
187 
114 
340 
235 

89 
144 
201 

22 
252 
324 

38 

56 
459 

96 
290 
379 

95 
318 
199 
298 
429 
133 
590 
365 
163 
341 
461 

47 
305 
119 

28 
231 
363 

73 
169 
142 

41 
229 
193 

63 

73 
408 

67 
381 
399 

46 

180 
165 
200 

69 

64 
237 
169 

53 
153 
467 
166 
240 
145 

47 
453 
291 

44 
288 
189 

23 
343 
332 
105 

24 

140 

48 

49 

34 

66 

204 

110 

16 

121 

169 

70 

147 

77 

32 

273 

198 

21 

119 

180 

59 

427 

346 

53 

96 

Pounds. 
1,570 
1,007 
1,687 

741 

810 
1,813 
1,708 

568 
2, 101 
2,553 

833 
1,957 
1,676 

844 
4, 227 
2,348 

715 
2,609 
2,594 

574 
4,307 
4,275 

672 

547 
3,771 

658 
3,116 
4,126 

576 
2,615 
1,552 
2,282 
3,189 
1,102 
4,034 
2,681 
1, 125 
2,4.52 
2,804 

936 
3,464 
1,924 

655 
1,742 
3,288 

727 
1,572 
1,347 

695 
2,114 
2,641 
1,067 

753 
3,797 
1,024 
3,298 
3,412 

859 

10 

9.5 
10 

9.8 
10 
10 
10 
10 
10 
10 
10 

9.4 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.8 
10 

8.6 
10 
10 
10 

8 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.6 
10 
10 

9.5 
10 
10 

Pounds. 
157 

2 

106 

3. 

168.7 

4 

5 

6.     

75.6 
81 
181.3 

170.8 

8. 

56.8 

9 

10 

210.1 
2.55. 3 

11 

65  1  71 
229  166 

83.3 

12 

208.2 

13 

14 

232 
121 
492 
157 
133 
383 
251 

61 
426 
384 

22 

65 
380 

70 
345 
313 

29 
188 

71 
177 
283 

87 

192 

55 

357 

112 

56 

241 

324 

99 

438 

524 

80 

50 

236 

121 

400 

385 

36 

198 

152 

139 

271 

128 

167.6 
84.4 

15 

16 

17 

18... 

422.7 
2:34.8 
71.5 
260.9 

19 

2.59.4 

20 

57.4 

21 

22 

430.7 
427.5 

23 

24. 

67.2 
54.7 

25 

285  1  430 

377.1 

26 

27 

28 

49 
206 
421 

25 

45 
217 
379 

46 

65.8 
311.6 
412.6 

29 

57.6 

30 

236  342 

261.5 

31 

215 
299 
387 
127 
424 
315 
138 
274 
339 
114 
314 
299 
52 
182 
326 

215 
243 
208 
146 
448 
310 
143 
403 
414 
222 
400 
211 
84 
226 
9«fi 

155.2 

32 

228.2 

33 

34 

325.4 
110.2 

35 

393  291 

298  213 

80  '     ?tfi 

469 

36 

268.1 

37 

112.5 

38 

246 
283 
135 
412 
287 

92 
171 
328 

52 
130 

97 

77 
250 
264 
162 
140 
337 

93 
336 
330 

91 

91 
154 
123 
268 
176 

85 
150 
220 

87 
149 
155 

91 
284 
330 

99 

68 
457 
166 
361 
400 

64 

245.2 

39 

350.5 

40 

59 
451 
157 

32 
163 
222 
107 
118 
106 

95 
147 
263 
135 
105 
443 

80 
415 
359 

92 

69 
430 
179 

32 

70 
510 

90 
228 
117 

78 
107 
247 
147 

54 
311 

45 
294 
254 

86 

93.6 

41 

346.4 

42 

192.4 

43 

65.5 

44 

174. 2 

45 

328.8 

46 

103  !  53 
190  i  958 

72.7 

47 

157.2 

48 

151 

74 

295 

299 

94 

90 

294 

92 

268 

397 

181 

32 

350 

310 

132 

54 

285 

94 

504 

471 

134.7 

49 

69.5 

50 

211.4 

51 

264.1 

52 

106. 7 

53 

78.4 

54 

379.7 

55 

102.4 

56 

347.1 

57 

341.2 

58 

51  1  •'^'' 

85.9 

„_ 

GATHERING    FKUIT    OF    SPRAYED    AND    UNSPRAYED    TREES.      109 

At  the  side  of  the  total  colunm  in  the  preceding-  table  is  given  a  col- 
umn showing  the  number  of  trees  in  each  row.  The  total  amount  of 
fruit  gathered  at  the  first  picking  from  each  row  has  been  divided  by 
the  number  of  trees  in  the  row,  giving  the  average  aniount  of  fridt 
picked  per  tree  for  each  row  of  the  block.  This  average  is  shown  in 
the  right-hand  column. 

In  the  table  which  follows  is  given  the  net  weight  of  fruit  gathered 
at  the  second  picking  from  each  tree  of  the  block  not  picked  clean  at 
the  tir.st  picking. 


Table  26. —  Weight  of  peaches  uf  second  picking  from  the  Lovell  trees  of  the  experiment 
block  of  the  Rio  Bonito  orchard,  gathered  in  the  fall  of  1895. 


Row  No. 


Weight  of  fruit,  in  pounds,  gathered  at  second 
picking  from  trees  Nos. — 


121 

6 

124 


13 

21 

6 

6 

18 

11 

18 

11 

28 


18 


1 
295 
33 
150 
212 
62 
63 
119 


23 


24 


10 


26 


10 


13 


28 


13 


16 


Total  net 
weight 
of  fruit 
in  row. 


Pounds. 

1,242 

343 

1,109 

255 

236 

452 

517 

107 

357 

415 

136 

146 

184 

84 

124 

152 

43 

91 

118 

74 

136 

146 

40 

52 

217 

14 

100 

137 

26 

2,526 

786 

1,136 

1,082 

222 

840 

393 

245 

424 

439 

173 

566 

198 

84 

265 

203 

47 

102 

92 

61 

55 

91 

64 

47 

266 

75 

92 

91 

43 


Number 
of  trees 
in  row. 


10 

9.5 
10 

9.8 
10 
10 
10 
10 
10 
10 
10 

9.4 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.8 
10 

8.6 
10 
10 
10 

8 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
9.6 
10 
10 
9.5 
10 
10 


Average 
weight 
per  tree. 


Pounds. 

124.2 
36.1 

110.9 
26 
23.6 
45.2 
51.7 
10.7 
35. 7 
41.5 
36.6 
15.5 
18.4 
8.4 
12.4 
15.2 
4.3 
9.1 
11.8 
7.4 
13.6 
14.6 
4 

5.2 
21.7 
1.4 
10 
13.7 
2.6 

252. 6 
78.6 

113.6 

110.4 
22.2 
97.6 
39.3 
24.5 
42.4 
54.8 
17.3 
56.6 
19.8 
8.4 
26.5 
20.3 
4.7 
10.2 
9.2 
6.1 
5.5 
9.1 
6.4 
4.9 

26.6 
7.5 
9.7 
9.1 
4.3 


110 


PEACH    LEAF    CURL:    ITS    NATURE    AND    TREATMENT. 


The  total  5deld  of  the  trees  and  rows  of  the  experiment  block  is 
shown  in  the  following-  table,  which  was  compiled  from  the  preceding 
records  of  fruit  gathered  at  the  first  and  second  pickings. 

Table  27. — Total  weight  of  peaches' of  first  and  second  pickings  gathered  from  the  Lovell 
trees  of  the  experiment  block  of  the  Rio  Bonito  orchard  in  the  fall  of  1895.  (a) 


Row  No. 


Total  weight  in  pounds  of  fruit  gathered  at  first  and  second  pickings  from  trees  Nos.  — 


1. 


I. 

3. 

4. 

230 

183 

340 

9.'> 

134 

236 

2Ah 

173 

298 

71 

173 

70 

74 

49 

146 

83 

253 

197 

276 

238 

197 

89 

30 

11 

2«7 

188 

216 

285 

357 

105 

76 

35 

97 

178 

111 

191 

205 

221 

70 

61 

114 

117 

363 

556 

253 

12;^ 

321 

87 

56 

66 

52 

251 

322 

256 

330 

381 

144 

102 

125 

109 

446 

483 

410 

552 

558 

257 

80 

88 

67 

56 

65 

48 

247 

414 

180 

121 

71 

16 

409 

446 

116 

404 

573 

298 

39 

99 

64 

;«9 

532 

525 

259 

160 

219 

284 

282 

333 

463 

371 

527 

190 

156 

53 

542 

300 

288 

248 

186 

127 

69 

82 

153 

220 

243 

•^96 

438 
95 

155 

m 

371 

423 

499 

249 

151 

157 

85 

117 

46 

168 

306 

206 

236 

314 

222 

99 

64 

107 

160 

148 

118 

155 

155 

136 

91 

78 

105 

284 

214 

161 

330 

288 

288 

99 

135 

141 

68 

72 

114 

478 

541 

460 

170 

108 

96 

361 

346 

442 

418 

277 

359 

64 

99 

92 

5. 


5. 

7. 

8. 

245 

394 

302 

111 

115 

181 

267 

315 

403 

165 

91 

100 

152 

159 

100 

117 

321 

222 

183 

211 

222 

151 

142 

52 

248 

315 

234 

327 

325 

297 

107 

145 

69 

167 

288 

168 

203 

244 

187 

114 

99 

127 

474 

580 

340 

216 

462 

263 

119 

63 

89 

2;S3 

296 

144 

364 

259 

212 

27 

36 

22 

431 

629 

252 

556 

469 

324 

95 

82 

38 

52 

53 

74 

424 

589 

488 

62 

115 

96 

425 

,   513 

306 

489 

489 

379 

102 

33 

95 

418 

434 

459 

282 

138 

222 

331 

316 

328 

477 

442 

448 

148 

92 

139 

543 

632 

684 

369 

365 

437 

111 

135 

187 

261 

308 

341 

451 

462 

475 

74 

53 

47 

262 

425 

326 

183 

236 

124 

58 

104 

40 

205 

154 

240 

341 

430 

389 

63 

44 

82 

148 

111 

178 

94 

182 

154 

73 

95 

43 

130 

118 

239 

220 

251 

203 

96 

43 

66 

75 

44 

82 

476 

402 

426 

171 

137 

93 

198 

244 

381 

312 

313 

425 

195 

109 

52 

10. 


Total. 


1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 
10. 
11. 
12. 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
20. 
21. 
22. 
23. 
24. 
25. 
26. 
27. 
28. 
29. 
30. 
31. 
32. 
33. 
34. 
35. 
36. 
37. 
38 
39. 
40. 
41 
42. 
43 
44 
45 
46 
47 
48 
49 
50 
51 
52 
53 
54 
55 
56 
57 
58 


129 

76 
243 

81 

42 
239 
148 
104 
290 
245 

72 
240 
2-55 
140 
525 
177 
144 
406 
261 

68 
438 
395 

28 

71 
403 

75 
345 
313 

29 
458 
111 
377 
396 

95 
482 
304 

92 
269 
309 
150 
459 
308 

99 
187 
347 

55 
140 
108 

82 
254 
276 
162 
147 
356 

93 
339 
331 

91 


259 

54 
308 

57 
134 
311 
301 

39 
314 
238 

83 
304 
184 

47 
474 
298 

88 
341 
362 

54 
498 
544 

62 

43 
458 

19 
166 
417 

65 
524 
176 
325 
253 
107 
593 
199 
242 
336 


69 
430 
179 

32 

70 
534 

90 
228 
117 

78 
107 
247 
147 

54 
311 

45 
294 
254 


422 
232 
308 
103 

87 
275 
199 

71 
179 
530 
184 
255 
159 

59 
475 
297 

51 
302 
202 

28 
396 
340 
107 

28 
285 

52 
222 
460 

25 
675 
408 
389 
468 
141 
570 
315 
138 
305 
369 
114 
335 
299 

52 
213 
359 
103 
215 
157 

79 
306 
314 
100 

90 
328 

92 
281 
327 

62 


308 
116 
236 

85 
103 
247 
250 

36 
187 
259 
101 
201 
132 

50 
311 
256 

30 
149 
197 

77 
460 
426 

65 
109 
500 

45 
268 
441 

51 
727 
363 
453 
426 
203 
528 
363 
187 
440 
443 
245 
500 
236 
106 
258 
319 

67 
228 
181 

32 
356 
315 
142 

54 
285 

94 
504 
487 

52 


2,812 
1,350 
2,796 

996 
1,046 
2,265 
2,225 

'675 
2,458 
2,968 

969 
2,103 
1,860 

928 
4,351 
2,500 

758 
2,700 
2,712 

648 
4,443 
4,421 

712 

599 
3,988 

672 
3,216 
4,263 

602 
5,141 
2,338 
3,418 
4, 271 
1,324 
4,874 
3,074 
1,370 
2,876 
3,243 
1,109 
4,030 
2, 122 

739 
2,007 
3,491 

774 
1,674 
1,439 

756 
2, 169 
2,732 
1,131 

800 
4,063 
1,099 
3,390 
3,503 

902 


a  For  plat  of  orchard  see  p.  69;  for  sprays  applied  see  p.  73. 

As  already  said,  after  the  weight  of  fruit  for  each  tree  of  a  row  had 
been  asc-ertained  and  recorded,  the  number  of  peaches  in  1<>0  pounds 
of  this  fruit  was  determined  by  counting.  From  several  picking- 
boxes  of  fruit,  coming  from  different  trees  of  the  row,  was  weighed 
out  100  pounds  of  peaches  fairly  representing  the  fruit  of  the  row. 
The  peaches  of  this  100  pounds  were  then  carefully  counted  and  the 
number  recorded.     This  was  done  both  foi  the  first  and  second  pick- 


GATHERING    FRUIT    OB^    SPRAYED    AND    UNSPRAYED    TREES.      Ill 


ings  aiul  for  the  sprayed  and  imspniyiMl  row.s.  Whore  less  than  loo 
pounds  of  fruit  was  oathcrod  tho  iHiinh(>r  of  peaches  ])er  100  pounds 
was  (h'terinined  by  countini;-  a  h'ss  weioht  of  fruit,  usually  .')(»  pounds. 
The  foUowin^i'  table  gives  the  results  of  this  work  for  both  (ii-st  and 
second  pickings: 

Table  28. — Xiuiihcr  of  peaches  per  100  pomtds;  wcujlil  uf  fruit  gulheral;  and  inimhcr  of 
peaches  thinned,  gathered,  and  set  by  the  trees  of  each  row  in  the  experiment  block  of  Ihr  I  Ho 
Bonito  orchard  in  1895.  (a) 


Number  of 

peaches  in  100 

pounds. 


03 


Pounds  of 
fruit — 


Number  of 
peaches  gath- 
ered at — 


Number  of 
peaches— 


-o  2 


a 

o 

'm 

O 

OQ 

fe 

1,242 

4,066 

343 

2,971 

1,109 

4,  SOS 

255 

2, 223 

236 

2, 4.54 

4.52 

5,040 

517 

4, 7S2 

107 

1, 602 

357 

6, 051 

415 

7,199 

136 

2,432 

146 

5, 538 

184 

4,911 

84 

2,  .583 

124 

13, 061 

152 

6,903 

43 

2,116 

91 

7,827 

118 

7,496 

74 

1, 665 

136 

13, 266 

146 

13, 6S0 

40 

1,989 

52 

1,597 

217 

10,710 

14 

1,S12 

100 

8.600 

137 

12,  om 

26 

1,596 

2,526 

7,636 

786 

4,718 

1,136 

6,709 

1,082 

9,280 

222 

3,196 

840 

13,111 

393 

7, 641 

245 

3,173 

424 

6, 915 

439 

8, 104 

173 

2,808 

.566 

9, 838 

198 

b,mo 

84 

1,919 

265 

.5,383 

203 

10,160 

47 

2,203 

102 

4,  .543 

92 

4,149 

61 

2,029 

55 

6,067 

91 

7,897 

64 

3,233 

47 

2,259 

266 

11,619 

75 

3,021 

92 

9,663 

91 

10,168 

43 

2,422 

o^ 


P  OJ 

Eh 


Average 
number  of 
peaehes  set 

per  tree. 


259 
295 
285 
300 
303 
278 
280 
282 
288 
282 
292 
283 

293  ' 
306 
309 
294 
296 
300 
289 
290 
308 
320 
296 
292 
284 
280  I 

276  : 

291  I 

277  j 

292  I 
304  , 

294  i 
291 
290  I 
325 
285  I 
282 
282 
289  • 
300 
284 
303 
293 
309 
309 
303 
289 
308 
292 
287 
299 
303 
300 
306 
295 
293 
298 
282 


288 

317 

310 

335 

323 

324 

326 

322 

323 

313 

316 

321 

312 

6  324 

362 

317 

6  327 

6  339 

6  340 

6  332 

6  314 

6  362 

6  344 

6  3.56 

6  368 

6  3.54 

6  360 

6  370 

6  360 

313 

326 

311 

335 

330 

345 

332 

330 

330 

328 

312 

339 

335 

6  304 

337 

346 

6  330 

3.56 

6  324 

6  312 

6  3(!(; 

6  3.56 

6  336 

6  325 

6  3.52 

6  334 

6  384 

6  370 

6  360 


1,570 
1,007 
1,687 

741 

810 
1,813 
1,708 

568 
2,101 
2,  .5.53 

833 
1, 9.57 
1,676 

844 
4, 227 
2,348 

715 
2, 609 
2,  .594 

.574 
4,307 
4,275 

672 

.547 
3,771 

658 
3,116 
4, 126 

576 
2, 615 
1,  .5.52 
2, 282 
3, 189 
1,102 
4,034 
2,681 
1,125 
2,4.52 
2,804 

936 
3,464 
1,924 

6.55 
1,742 
3,2*8 

727 
1,.572 
1,347 

695 
2,114  I 
2,641  I 
1,067  I 

7.53  I 
3,797  : 
1,024 
3, 298 
3, 412 

,S.59 


3,  .577 

1,087 

3,438 

8.54 

762 

1,4(H 

1,68.^, 

345 

1, 153 

1,299 

430 

469 

574 

272 

449 

482 

140 

308 

401 

246 

427 

529 

138 

185 

799 

50 

360 

507 

94 

7,906 

2,562 

3,533 

3, 625 

733 

2,898 

1,305 

809 

1,399 

1,440 

.540 

1,919 

663 

2.55 

893 

702 

155 

363 

298 

190 

201 

324 

215 

153 

936 

250 

3.53 

3:i7 

1.55 


7,643 
4, 058 
8, 246 
3,077 
3,216 
6,504 
6,467 
1,947 
7, 204 
8,498 
2,862 
6,007 
5, 485 
2, 855 

13,  .510 

■  7, 385 
2, 2.56 
8, 135 
7,897 
1,911 

13,693 

14,209 
2, 127 
1,782 

11,. 509 
1,892 
8,960 

12,  .513 
1,690 

15, 542 
7, 280 

10,242 

12, 905 
3,929 

16,009 
8,946 
3, 982 
8,314 
9,544 
3,348 

11,757 
0,493 
2,174 
6,276 

10,862 
2,3.58 
4, 90C) 
4,447 
2,219 
6,268 
8,221 
3,448 
2,412 

12,  .555 
3,271 

10, 016 

10,  .505 
2,  .577 


5,442 
'4,'829 


2, 3.52 
2, 265 


3,863 
4, 3.52 


2,730 
1,841 


7,762 
2, 401 


3, 024 
3,616 


8,470 
7, 269 


5, 128 
5, 742 


10,208 


3,269 
7,360 


9,730 
4,896 


3,318 
5,821 


5,953 


773 
3, 951 


675 


2,985 


5,  .568 


5, 659 
5, 2.51 


13,085 
4, 0.58 

13, 075 
3,077 
3,216 
8, 8.56 
8, 732 
1,947 

11,067 

12, 8.50 
2, 862 
8,737 
7, 326 

2. 8.55 
21,272 

9,786 

2. 2.56 
11,1.59 
11,. 513 

1,911 

22, 163 

21,478 

2, 127 

1,7.82 

17,2.56 

1,892 

14, 088 

18, 2.55 

1,690 

25, 7.50 

7, 2.S0 

13,  .511 

20, 26.^ 

3, 929 

25, 739 

13,  .841' 

3, 982 

11,632 

15, 365 

3, 348 

17,710 

6, 493 

2,174 

7,049 

14,813 

2, 3.58 

4,906 

5,122 

2,219 

6, 268 

11,206 

3, 448 

2,412 

18, 123 

3,271 

1.5,675 

15, 7.5(i 

2,  .577 


10 

9.5 
10 

9.8 
10 
10 
10 
10 
10 
10 
10 

9.4 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.8 
10 

8.6 
10 
10 
10 

8 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.6 
10 
10 

9.5 
10 
10 


1,308 

i',m 


886 
873 


1,107 
1,285 


929 
733 


2,127 
979 


1,116 
1,1.51 


2,216 
2,148 


1,726 


1,409 
1,825 


2,  .575 


1,351 
2,068 


2,993 
1,384 


1,163 
1,921 


1,771 
649 


705 
1,481 


491 
512 


627 
1,120 


1,812 


1,6.50 
1,576 


a  For  plat  of  orchard  see  p.  09;  for  sprays  applied  see  p.  73. 

6  Number  calculated  from  a  less  weight  than  100  pounds,  usually  from  50  pounds 


112    PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

Following  the  lig-ures  in  the  above  table  which  .show  the  number  of 
peaches  in  100  pounds  of  fruit  are  those  giving  the  number  of  pounds 
of  fruit  gathered  at  the  first  and  second  pickings.  From  these  four 
columns  of  figures  has  been  calculated  the  number  of  peaches  gathered 
from  the  trees  of  each  row  of  the  block  for  both  the  first  and  second 
pickings.  By  adding  these  numbers  the  total  number  of  peaches 
matured  bv  the  trees  of  each  row  was  quite  accurately  determined. 
To  this  amount  is  now  added  the  number  of  peaches  thinned  from  the 
trees,  where  thinning  was  required,  the  grand  total  representing  the 
number  of  peaches  firmly  set  by  the  trees  of  each  row.  By  dividing 
this  grand  total  by  the  immber  of  trees  in  a  row  it  has  been  possible 
to  show  the  average  number  of  peaches  set  per  tree  on  both  sprayed 
and  unsprayed  trees,  and  for  ever}^  row  in  the  experiment  block. 

COMPARATIVE  QUANTITY,    QUALITY,    AND    CASH    VALUE    OF    FKUIT    FROM 
SPRAYED   AND   UNSPRAYED   TREES. 

(Pis.  XI  ami  XII.) 

The  actual  yield  in  pounds  of  peaches,  the  qualit}",  and  the  cash 
value  of  the  fruit  produced  by  the  sprayed  and  unsprayed  trees  of  the 
experiment  rows  of  the  Rio  Bonito  orchard  in  the  season  of  1895  are 
full}'^  and  accurately  shown  in  the  table  which  follows.  This  table 
gives  a  full  record  of  the  yield  as  it  was  taken  in  the  orchard,  and  the 
results  are  of  the  greatest  value  from  a  practical  standpoint,  convey- 
ing an  accurate  idea  of  the  cash  gain  resulting  from  this  spray  work. 
If  the  reader  will  compare  the  average  value  of  the  fruit  produced  by 
the  sprayed  trees  of  row  21,  for  example,  with  that  of  the  fruit  pro- 
duced by  the  unsprayed  trees  of  row  20,  some  conception  of  the 
possible  gains  resulting  from  thorough  spraying  may  be  obtained.  In 
studying  this  table,  it  should  be  remembered  that  the  results  shown 
were  obtained  from  the  use  of  35  different  f ormulte  and  spra3^s.  Some 
of  the  sprays  were  of  little  value,  others  of  medium  value,  etc.,  hence 
the  gains  shown  for  the  entire  block  are  far  below  what  they  would 
have  been  had  the  trees  of  each  of  the  rows  been  sprayed  with  such 
sprays  as  those  used  upon  rows  21,  22,  or  others  of  the  better-yielding 
rows  of  the  block. 


DESCRIPTION  OF   PLATE   XI. 

Experiments  at  Biggs,  Cal.  (Siili)hur,  lime,  and  salt.)  Looking  west  between  rows 
2  and  3,  May  14,  1895.  Row  2  was  unsprayed;  row  3  was  sprayed  before  blooming 
with  15  pounds  sulphur,  20  pounds  lime,  5  jiounds  salt,  and  45  gallons  of  water. 
The  average  value  of  fruit  matured  jjer  tree  in  row  2  was  $1.96  and  in  row  3  i5i3.90. 
The  spray  used  showed  a  net  gain  from  the  treatment,  as  determined  by  the  compar- 
ative value  of  the  peaches  set  by  the  trees  of  both  rows,  of  216  per  cent  (p.  117) . 


Bull.  20,  Div.  Veg.  Pnyi.  8c  Patn.,  U.  S.  Dept.  of  Agiicultuie. 


Plate  Xi. 


DESCRIPTION  OF   PLATE   XII. 

Experiments  at  Biggs,  Cal.  (Sulplinr  and  lime.)  Looking  west  between  rows  9 
and  10,  INIay  14,  1895.  Both  rows  were  sprayed  before  l)looming.  Row  9  was  treated 
with  10  pounds  sulphnr,  20  pounds  lime,  and  45  gallons  of  water,  and  row  10  with 
10  pounds  sulphur,  8  pounds  lime,  and  45  gallons  of  water.  Row  8,  adjoining  row  9 
at  the  south,  and  row  11,  adjoining  row  10  at  the  north,  were  untreated.  The  aver- 
age value  of  fruit  matured  i^er  tree  on  row  9  was  $3.35,  and  on  row  8  only  91  cents. 
The  average  value  of  fruit  matured  per  tree  on  row  10  was  $3.90,  and  on  row  11,  $1.35. 
As  determined  by  the  comparative  value  of  the  peaches  set  by  the  trees,  the  spray 
used  on  row  9  showed  a  net  gain  over  row  8  of  457  per  cent,  and  that  used  on  row 
10  showed  a  net  gain  over  row  11  of  337  per  cent  (p.  117) .  It  may  be  seen  that  the 
lower  limbs  are  not  as  thickly  covered  with  foliage  where  the  sulphur  sprays  are 
used  as  where  the  copper  sprays  are  used.  This  is  especially  true  where  the  former 
is  applied  too  late  or  too  strong.      (See  PI.  XI.) 


Bull.  20,  Div.  Veg.  Pnys.  &  Path  ,  U.  S.  Dept.  of  Agriculture. 


Plate  XII. 


COMPARATIVE    QUANTITY,    QUALITY,    AND    VALUE    OF    ERUIT.        113 


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19093— No.  20 8 


114 


PEACH   LEAF    CUEL".    ITS    NATURE    AND   TREATMENT. 


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Bull.  20,  Div,  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XIII. 


DESCRIPTION  OF   PLATE  XIII. 

Experiments  at  Bigg^i,  Cal.  (Bordeaux  mixture.)  Looking  west  between  row's 
20  and  21,  May  11,  1895.  Row  20  was  unsprayed ;  row  21  was  sprayed  l)eiore  bloom- 
ing witli  5  pounds  copper  sulphate,  5  pounds  lime,  and  45  gallons  of  water.  The 
average  value  <jf  fruit  matured  jier  tree  in  row  20  was  90  cents;  in  row  21,  $6.19.  The 
spray  used  on  row  21  showed  a  net  gain  over  row  20,  as  determined  Ijy  the  com- 
parative value  of  the  peaches  set  by  the  trees  of  both  rows,  of  1,028  per  cent  (p.  117) . 


Bu'.l.  20,  Div.  Veg.  Phy^.  &  Path,,  U.  S.   Dept.  of  Agriculture. 


Plate  XIV. 


DESCRIPTION  OF  PLATE  XIV. 

Experiments  at  Bigjis,  Cal.  (Eau  celeste.)  Looking  west  between  rows  20  and  27, 
.May  n,  1895.  Row26  unsprayed;  row  27  sprayed  before  bloondng  with  4  pounds  cop- 
per sulphate,  8  \nnts  ammonia,  and  45  gallons  of  water.  Average  value  of  fruit 
matured  per  tree  in  row  26  was  90  cents;  in  row  27,  $4.32.  The  spray  used  on  row 
27  showed  a  net  gain  over  row  26,  as  determined  by  the  comparative  value  of  the 
peaches  set  by  the  trees  of  both  rows,  of  662  per  cent  (p.  117) . 


Bu:l.  20,  Div.  Veg.  Phys   &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XV. 


O    Tf 


5     - 


DESCRIPTION  OF  PLATE  XV. 

Experiments  at  Biggs,  Cal.  (Modified  can  celeste.)  Looking  east  between  rows 
34  and  35,  May  14,  1895.  Row  34  unsprayed;  row  35  sprayed  l)efore  l)looniing 
with  4  pounds  copper  sulpliate,  5  pounds  sal  soda,  3  pints  ammonia,  and  45  gallons 
of  water.  The  average  value  of  fruit  matured  per  tree  in  row  34  was  $1.84;  in  row  35, 
$8.05.  The  spray  used  on  row  35  showed  a  net  gain  over  row  34,  as  determined  by 
the  comparative  value  of  the  peaches  set  bv  the  trees  of  both  rows,  of  608  per  cent 
(p.  118). 


INFLUENCE  OF  SPRAYS  ON  THE  FRUITING  OF  THE  TREES.         115 

COIVIPARATIVE  VALUE  OF  SPRAYS  IN  RELATION  TO  FRUIT. 

(Pis.  XIII,  XIV,  and  XV.) 

A  revieTT  of  the  preceding  table  will  show  that  no  account  has  been 
taken  there  of  the  peaches  thinned  from  the  trees,  and  for  this  reason 
the  results  given  in  dollars  and  cents  for  the  different  rows  can  not  be 
taken  as  representing  the  full  comparative  value  of  the  sprays  used. 
The  value  of  a  spray  in  controlling  curl,  so  far  as  quantity  of  fruit  is 
concerned,  should  be  based  upon  its  power  to  prevent  the  fall  or  loss 
of  fruit  from  the  disease.  A  spray  may  enable  a  tree  to  set  more 
fruit  than  it  can  carry  to  maturity'  in  a  favorable  season,  but  the  value 
of  the  spray  should  not  be  decided  from  the  amount  of  the  crop  after 
thinning.  This  will  be  evident  from  a  consideration  of  the  fact  that 
in  many  years  the  trees  may  not  set  more  peaches  than  can  be  properly 
matured  without  thinning.  In  such  cases  it  would  be  the  spray  that 
enabled  the  trees  to  set  and  hold  the  greatest  number  of  peaches  in 
the  presence  of  curl  which  would  prove  of  the  highest  value  to  the 
grower.  A  less  effective  spray  would  not  enable  the  trees  to  set  and 
hold  a  full  crop.  It  is  thus  seen  that  the  comparative  value  of  several 
spraj'S  rests  in  their  power  to  prevent  the  fall  of  the  greatest  num- 
ber of  peaches  from  disease,  this  being,  of  course,  where  other  influ- 
ences of  the  spraj's  are  equal.  Thinning  is  necessary  only  when  the 
trees  can  not  carry  all  the  fruit  set,  or  when  it  is  desired  to  improve  the 
size  and  quality  of  the  fruit,  and  it  bears  no  direct  relation  to  the 
value  of  a  spray  in  preventing  curl. 

In  view  of  the  preceding  facts,  a  table  has  been  prepared  embodying 
those  features  of  the  fruit  records  bv  which  the  comparative  value  of  all 
the  sprays  used  may  be  determined. 

To  show  the  full  comparative  value  of  all  influences  of  each  spray 
upon  the  fruit,  it  has  also  been  necessary  to  consider  the  quality  as 
well  as  the  number  of  peaches  and  weight  of  same.  To  obtain  the 
ultimate  comparative  value  of  the  sprays  the  writer  has  been  obliged 
to  treat  the  thinned  peaches  as  if  matured,  assigning  them  the  same 
value,  in  proportion  to  number,  as  the  matured  fruit.  There  is  also 
one  other  calculation  in  the  table  which  requires  explanation.  A  con- 
siderable percentage  of  the  better  quality  of  fruit  was  picked  while 
still  immature.  This  fruit  is  tabulated  as  that  for  the  Oakland  can- 
nery. It  was  necessary  to  gather  this  fruit  while  still  hard  so  that  it 
would  arrive  at  the  Oakland  cannerv  in  good  condition.  By  weighing 
a  large  number  of  matured  peaches  and  an  equal  number  of  peaches 
as  picked  for  the  Oakland  cannery  it  was  learned  that  the  Oakland 
fruit  should  be  increased  by  11  per  cent  to  make  it  equal  in  weight  to 
mature  fruit.  This  has  been  done,  so  that  the  quantity,  quality,  and 
full  comparative  value  of  all  fruit  considered  could  be  accurately 
determined. 


116         PEACH    LEAF    CURL:    ITS    NATURE    AND   TREATMENT. 

It  has  been  possible  in  the  manner  just  outlined  to  calculate  the 
total  comparative  value  of  all  fruit  set  by  the  trees  of  each  row,  as 
determined  by  the  actual  cash  value  of  fruit  of  equal  quality  when 
matured.  By  dividing  this  sum  by  the  number  of  trees  in  the  row 
the  average  comparative  value  per  tree  of  all  fruit  set  is  shown,  both 
for  sprayed  and  unsprayed  rows.  While  these  average  values  do  not 
represent  the  money  actually  obtained,  as  in  the  case  of  the  preceding 
table,  they  accurately  show  the  average  values  for  comparison  of  all 
fruit  set  b}^  the  trees,  as  determined  by  the  market  price  of  that  fruit 
which  the  trees  were  able  to  bring  to  maturity.  For  these  reasons 
the  figures  for  the  different  rows  may  1)e  rightly  compared,  and  they 
fairly  determine  the  comparative  values  of  the  35  sprays  tested  in  the 
block,  so  far  as  those  values  relate  to  the  quantity  and  quality  of  the 
fruit. 

To  further  facilitate  the  comparison  of  the  values  of  the  sprays  in 
increasing  the  quantity  and  quality  of  fruit,  as  determined  by  the  cash 
value  of  such  fruit  when  matured,  the  results  have  been  reduced  to 
average  net  gain  per  cent  of  the  sprayed  trees  of  each  treated  row  over 
those  of  the  adjoining  unsprayed  row.  For  illustration,  it  may  be  seen 
that  in  row  30,  spraved,  the  average  calculated  value  of  all  fruit  set 
per  tree  would  have  been  when  matured  §12.62;  in  row  31,  unsprayed, 
$3.43.  Deducting  the  calculated  average  value  of  the  fruit  set  on  the 
trees  of  row  31  from  that  set  on  the  trees  of  row  30,  there  is  shown  an 
excess  of  $9.19  in  favor  of  the  trees  of  the  sprayed  row,  and  by  divid- 
ing this  excess  by  $3.43,  the  calculated  average  value  of  fruit  set  by 
the  trees  of  the  unsprayed  row,  there  is  shown  to  be  a  net  gain  of  268 
per  cent  resulting  from  the  use  of  the  spra}^  applied  to  the  trees  of 
row  30.  The  gain  per  cent  has  in  this  manner  been  calculated  for 
every  spray  tested  in  the  block,  and  it  may  be  seen  that  on  row  21  the 
spray  gave  a  net  gain  of  1,028  per  cent. 


COMPAKATIVE  VALUE  OF  SPEAYS  IN  RELATION  TO  FRUIT. 


117 


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118 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


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INFLUENCE  OF  SPRAYS  ON  THE  FRUITING  OF  THE  TREES.        119 
COMPARATIVE    SIZE     OF     FRUIT     ON     SPRAYED     AND     UNSPRAYED     TREES. 

Owing  to  the  fullness  of  the  records  obtained  relative  to  the  weight 
and  number  of  peaches  gathered  from  the  sprayed  and  unspraved 
trees  in  the  present  experiments,  it  is  possible  to  learn  the  compara- 
tive average  weight  of  the  fruit  produced  on  treated  and  untreated 
trees.  It  might  seem  that  the  unspraved  trees,  having  to  mature  on 
an  average  291.3  peaches  per  tree,  would  jield  larger  fruit  than  the 
sprayed  trees,  which  had  to  mature  949.2  peaches  per  tree;  in  other 
words,  that  the  increased  number  of  peaches  upon  sprayed  over 
uusprayed  trees  would,  to  a  considerable  extent,  be  counterbalanced 
by  an  increase  in  the  size  of  the  fruit  on  the  lightly  loaded  unspraj^ed 
trees.  It  has  been  found,  however,  that  w^here  the  conditions  for  vig- 
orous growth  of  a  tree  are  present,  and  where  the  fruit  upon  a  tree  is 
so  thinned  that  the  tree  is  not  overloaded,  the  peaches  of  the  full- 
bearing  tree  are  practically  as  large  when  mature  as  are  those  of  the 
tree  which  has  lost  much  of  the  crop  from  curl.  The  following  table 
has  been  compiled  from  the  facts  in  hand  upon  this  matter.  It  is 
shown  in  this  table  that  the  fruit  from  the  sprayed  trees  averaged 
for  the  whole  block  (315.3  trees)  299.0311:  peaches  per  100  pounds,  and 
the  fruit  from  the  unsprayed  trees  averaged  for  the  whole  block 
(228.9  trees)  299.0312  peaches  per  100  pounds.  This  shows  that  the 
gain  in  size  of  peaches  on  unsprayed  trees  over  those  on  sprayed  trees, 
as  determined  by  the  average  number  of  peaches  to  100  pounds,  is 
foVoiTTF  per  cent,  or  only  about  ^oVsj  of  1  per  cent.  This  amounts  to 
nothing  from  a  practical  standpoint. 

Table  31. — Size  of  fruit  on  sprayed  and  unsprayed  trees  as  determined  by  the  average 
number  of  peaches  per  100  pounds. 


Num- 
ber 

of 
trees 

in 
block 


Fruit 

produced  1 

by  all  trees  I 

of  block. 


Average 

production 

per  tree. 


First 
pick- 
ing. 


Sec- 
ond 
I)ick- 
ing. 


First 
pick- 
ing. 


Sec- 
ond 
pick- 
ing. 


Average  number  of 
peaches — 


Per 
100  pounds. 


First 
pick- 
ing. 


Sec- 
ond 
pick- 
ing. 


Per  tree. 


Proportion-I 

ate 
percentage  I 
yield       | 

of  trees,     i 


Average 

per- 
centage 
of  gain 
in  size 
of  fruit 


First 
pick- 
ing. 


Sec- 
ond 
pick- 
ing. 


First 
pick- 
ing. 


Sec- 
ond 
pick- 
ing. 


Aver- 
age 
num- 
ber of 

peachesi  ,„  „„ 
per  luu  I  „r,_„,,p^ 
Dounds  *P™>ea 
^  \:zr  trees  over 


per 
tree. 


that  of 

sprayed 

trees. 


Sprayed 

Unsprayed 


315.3  9.5,094 


ib.s.     LU. 


228.9 


19,035 


14,504 


3,257 


Lhz. 
275.4 


83.2 


Lbs. 
42 


293.2 
293.6 


337.4 
330.8 


807.6 
244.3 


13.2 
14.6 


299.0344 
299.0312 


It  should  not  be  understood  by  the  above  that  a  crop  of  950  peaches 
draws  no  more  heavily  upon  a  tree  than  a  crop  of  3()0  peaches  when 
other  conditions  are  equal.  All  observation  tends  to  show  that  such 
is   not  the   case.      A   tree    too    heavily   loaded   will    often    produce 


120  PEACH    LEAF    CURL:    ITS    NATURE    AND    TREATMENT. 

much  smaller  fruit  than  a  properl}'  thinned  tree,  even  upon  exceed- 
ingly rich  soil.  The  facts  given  in  both  the  preceding  text  and  table 
show  clearly,  however,  that  the  severe  attaclc  of  curl  in  the  spring  of 
1895  drew  upon  the  vitality  of  the  unsprayed  trees  as  heavily  as  did 
the  excess  of  65;)  peaches  each  on  the  sprayed  trees.  Otherwise  stated, 
the  trees  averaging -300  peaches  were  drawn  upon  as  heavily  by  the 
attack  of  curl,  combined  with  the  maturing  of  300  peaches,  as  were 
the  sprayed  trees  in  maturing  950  peaches.  If  this  had  not  been  the 
case,  the  unsprayed  trees  would  have  better  nourished  their  crop,  and 
would  have  produced  larger  and  heavier  fruit  than  those  which  were 
sprayed.  These  facts  should  receive  the  attention  of  all  thoughtful 
growers,  as  no  one  can  afford  to  have  his  trees  drawn  upon  to  the 
extent  of  two-thirds  of  a  crop  of  peaches  without  return,  even  when 
frost  or  other  causes  would  not  have  allowed  him  a  crop  on  sprayed 
trees.  To  permit  trees  thus  to  suffer  from  curl  even  in  such  a  year 
would  be  equivalent  to  draining  them  of  much  vitality,  even  though 
the}^  failed  to  show  this  drain  in  the  reduction  of  wood  or  fruit  liuds 
for  the  ensuing  year.  But  it  has  already  been  shown  that  a  marked 
reduction  in  the  number  and  quality  of  fruit  l>uds  is  a  result  of  a 
spring  attack  of  curl.  The  soil  is  also  certain  to  sustain  an  unnec- 
essary drain  upon  its  resources. 

Another  phase  of  this  subject  is  made  clearer  by  the  above  table. 
There  are  very  manj"  varieties  of  peaches  so  resistant  to  leaf  curl  that 
the  fruit  does  not  drop,  even  when  a  large  percentage  of  the  leaves 
are  lost.  Man}-  growers  leave  such  varieties  unsprayed,  thinking  that 
the  saving  of  the  fruit  is  the  all-important  point,  and  that  the  loss  of 
the  spring  foliage  alone  does  not  warrant  the  spraying  of  such  varie- 
ties. The  above  facts  will  show  the  error  of  such  deductions.  When 
the  loss  of  the  foliage  upon  the  Lovell  is  equal  to  the  drain  upon  the 
tree  brought  about  in  maturing  two-thirds  of  a  crop,  the  loss  of  the 
foliage  upon  a  semiresistant  variety  must  be  approximatel}"  the  same. 
This  drain  will  be  apt  to  show  also  in  the  size  and  weight  of  the  fruit, 
if  not  in  the  number  of  peaches.  Certainly  no  grower  is  warranted 
in  leaving  any  varietj"  unspraj^ed  simpl}'  because  that  variety  holds  its 
fruit  in  spite  of  the  loss  of  foliage.  The  trees  have  suffered  in  such 
a  case,  and  the  orchardist  can  scarcely  avoid  feeling  the  loss  in  the 
reduced  vigor  of  his  trees,  the  reduced  weight  and  size  of  his  fruit, 
and  the  added  drain  upon  his  soil. 

COLOR   OF    SPRAYED    AND    UNSPRAYED    FRUIT. 

The  Lovell  peach  is  normally  a  fruit  of  fine  color,  but  under  the 
action  of  certain  of  the  sprays  used  its  color  was  greatly  heightened. 
In  observing  this  action  of  the  spra3\s  no  color  scale  was  used,  but  the 
marked  brightening  on  certain  sprayed  rows  was  too  distinct  to  be 
mistaken  b}'^  the  most  careless  observer.     This  heightening  of  color 


METHOD    OF    THINNING    AND    COST    OF    PICKING    PEACHES.         121 

was  not  due  to  excess  or  lack  of  crop,  for  it  was  distinct  on  l)oth 
heavily  and  lightly  loaded  trees,  where  the  fruit  was  of  medium  size 
and  where  it  was  exceptionally  large.  l)ut  was  due  to  the  use  of  the 
copper  sprays,  especially  of  the  stronger  Bordeaux  mixtures  applied. 
Here  is  another  advantage  in  the  use  of  the  copper  salts.  This  increase 
in  color  would  certainly  mean  dollars  to  the  grower  where  the  fruit 
was  placed  on  the  market  in  competition  with  unsprayed  fruit,  even 
of  the  same  variety.  The  writer  regrets  that  a  color  scale  could  not 
have  been  used  in  this  connection,  so  that  the  true  heightening  of 
color  could  be  stated,  but  the  contrast  between  sprayed  and  unsprayed 
fruit,  where  the  spraying  was  done  with  the  Bordeaux  mixture,  was 
observed  and  discussed  by  many  who  had  this  fruit  to  handle. 

METHOD    OF    THINNING    AND    COST    OF    PICKING    PEACHES. 

THIXXIXG  BY  HAND  AND  BY  Cl'RL. 

An  argument  advanced  bv  certain  peach  growers  and  requiring  con- 
sideration is  that  a  moderate  spraying  under  ordinary  conditions  is 
sufficient.  By  avoiding  too  thorough  work  enough  curl  is  allowed  to 
develop  to  cause  the  dropping  of  one-fourth  to  one-half  of  the  peaches 
being  set  by  the  tree.  If  soil  conditions  are  favorable  it  is  thought 
the  trees  will  still  retain  a  sufficient  crop,  and  the  expense  of  thinning 
will  be  avoided. 

At  first  thought  the  plan  here  suggested  might  seem  the  easiest  and 
cheapest  waj'  of  thinning  fruit.  A  consideration  of  all  points  involved 
will  show,  however,  the  faults  of  this  method.  To  do  effective  pre 
ventive  spraying  against  curl  the  spray  must  be  applied  to  the  dormant 
tree,  and  to  judge  of  the  severity  of  a  coming  attack  of  curl  before 
growth  begins  is  too  uncertain  a  method  to  warrant  the  indorsement  of 
practical  growers.  All  influencing  conditions  may  appear  to  favor  a 
light  attack  of  curl  till  after  the  spraying  is  completed,  when  a  sudden 
change  of  temperature  or  a  cold  rain  may  develop  a  severe  attack 
within  the  course  of  a  few  days.  Under  such  conditions,  incomplete 
or  light  spray  work  may  cost  the  grower  the  major  portion  of  his 
crop. 

In  case  the  severitv  of  curl  is  about  as  presupposed,  the  numl^er 
of  peaches  remaining  on  the  tree  being  about  what  the  tree  should 
carry,  it  is  still  very  probable  that  the  grower  has  sustained  a  loss  in 
the  stoppage  of  growth  of  wood  and  fruit  and  in  the  fall  of  foliage 
equal  to  or  above  the  expense  of  thinning.  There  is  also  a  difference 
between  hand-thinned  trees  and  those  thinned  by  curl.  This  disease 
is  local  in  its  action,  not  general.  If  one  branch  in  the  midst  of  dis- 
eased branches  is  thoroughly  spraved  it  will  hold  its  fruit,  while  the 
peaches  will  fall  from  those  not  sprayed.  This  will  show  that  the 
peaches  of  a  diseased  tree  are  not  thinned  evenly,  as  the  disease  is  fre- 
quently not  uniformly  distributed  over  all  branches  of  the  tree.     Then 


122  PEACH   LEAF    CUKL".    ITS    NATURE    AND    TREATMENT. 

the  fruit  is  for  the  most  part  nourished  by  the  foliage  of  the  branch 
which  bears  it,  and  hence  if  the  disease  is  not  equally  distributed  the 
foliage  will  be  unequally  distributed  and  the  fruit  unequally  nourished. 
One  portion  of  a  tree  may  have  an  excess  of  fruit,  even  to  the  break- 
ing of  limbs,  while  another  portion  shows  a  deficiency.  Besides  the 
unequal  thinning  of  fruit  on  different  portions  of  a  tree,  arising  from 
the  unequal  action  of  curl  over  the  tree  as  a  whole,  there  will  also 
appear  an  unequal  thinning  of  the  fruit  of  individual  branches.  In 
this  respect,  one  of  the  prime  objects  of  hand  thinning,  the  equalizing  of 
the  fruit  distribution  upon  the  branches,  is  lost  when  the  thinning  is 
caused  by  curl.  Such  fruit  as  remains  upon  the  curl-thinned  branches 
is  apt  to  be  largely  toward  the  ends  of  the  limbs. 

The  statements  here  made  respecting  the  local  action  of  the  disease 
and  the  local  nourishing  of  the  fruit  upon  a  limb  or  portion  of  a  tree, 
are  known  to  be  correct,  and  have  been  established  by  a  series  of  care- 
fully conducted  experiments  on  sprayed  halves  of  trees.  The  details  and 
results  of  this  work  are  given  in  the  concluding  section  of  this  chapter. 

COST    OF    PICKING    PEACHES. 

When  considering  the  picking  and  sorting  of  peaches  from  sprayed 
and  unsprayed  trees  a  marked  difference  is  noted  in  cost  in  favor  of 
those  sprayed.  In  the  Rio  Bonito  orchard,  where  our  experimental 
work  was  prosecuted,  it  has  cost  the  proprietors  '^1  per  ton  to  pick 
fruit  from  fully  loaded  sprayed  trees.  In  contrast  to  this  the  cost 
of  picking  and  sorting  the  fruit  of  the  unsprayed  trees  just  north  of 
the  experiment  block,  in  the  summer  of  1S9.5,  was  $3  per  ton.  This 
was  on  account  of  the  scattered  condition  of  the  fruit  on  these  trees, 
which  were  affected  by  curl  in  the  spring  like  the  control  trees  of  the 
experiment  block.  This  cost  per  ton  was  calculated  with  wages  at  Bl 
per  day,  the  men  boarding  themselves,  and  where  one  sorter  to  five 
pickers  was  employed.  We  have  here  a  difference  of  $2  per  ton  in  the 
cost  of  picking  and  sorting  fruit  from  sprayed  and  unsprayed  trees. 
This  added  expense  on  unsprayed  trees  arises,  of  course,  through  the 
necessity  of  picking  over  a  greater  expanse  of  tree  and  orchard  surface 
to  obtain  a  given  amount  of  fruit.  It  is  l^elieved  that  in  this  single 
item  of  picking  the  fruit  enough  is  saved  to  more  than  cover  the  expense 
of  spraying  the  trees  and  thinning  the  fruit. 

THE  LOCAL  ACTION  OF  CURL  ON  FOLIAGE  AND  FRUIT. 

RECORDS   OF   TREES    SPRAYED    ON    ONE    SIDE. 

The  study  of  the  habits  of  Exomcus  defor/nans  and  its  influence  upon 
its  host  led  to  the  following  investigation  into  the  localization  of  the 
parasite  upon  the  tree  and  its  local  rather  than  general  effects. 


Bull.  20,  DIv.  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XVI. 


DESCRIPTION  OF  PLATE  XVI. 

Fig.  1  shows  the  condition  of  the  trees  sjirayed  on  one  side  (considered  in  the  text, 
p.  123).  The  right  side  of  the  tree  shown  was  sprayed  with  Bordeaux  mixture,  the 
left  side  was  unsprayed.      (Compare  with  Pis.  XVII,  XVIII,  and  XIX.) 

Fig.  2  shows  the  condition  of  the  tree  sprayed  on  one  side  after,  curl  had  largely 
denuded  the  unsprayed  half  at  the  left. 


LOCAL    ACTION    OF    CURL    ON    FOLIAGE    AND   FRUIT. 


123 


Just  north  of  the  experiment  block,  in  the  continuation  of  the  same 
orchard,  was  selected  a  row  of  6  trees  for  treatment  on  one  side.  The 
spray  used  on  half  of  each  of  the  first  three  trees  from  the  east  was  the 
standard  Bordeaux  mixture  recommended  1)y  the  Department,  viz,  6 
pounds  copper  sulphate,  4  pounds  (quicklime,  and  45  gallons  of  water. 
The  spray  used  on  the  following  three  trees  was  lime  and  sulphur,  con- 
sisting of  10  pounds  sulphur,  2(»  pounds  lime,  and  -15  gallons  of  water. 
In  doing  this  spraying  an  effort  was  made  to  treat  only  one-half  of 
each  tree.  Each  tree  was  first  examined,  and,  in  some  instances  at  least, 
a  large  canvas  stretched  through  it  in  such  a  manner  as  to  divide  it  as 
nearly  as  possible  into  two  equal  parts.  All  the  branches  on  one  side 
were  thoroughly  sprayed,  the  canvas  preventing  any  of  the  spray 
reaching  the  limbs  of  the  other  half.  In  this  way  the  half  of  each  of 
three  trees  was  spraj^ed  with  each  of  the  above-mentionel  sprays. 

A  photograph  showing  the  appearance  of  one  of  these  trees  shortly 
after  treatment  is  shown  in  PL  XVI. 

]Mav  10  and  18, 1895,  when  curl  had  reached  its  highest  development, 
careful  estimates  of  the  loss  of  foliage  were  made  for  the  sprayed  and 
unspra3'ed  sides  of  the  6  trees  used  in  the  experiment.  The  following 
table  shows  the  results  of  these  estimates: 


Table  32. — Foliage  lost  from  sprayed  and  unsprayed  halves  of  trees. 


Percentage  of  leaves  which  fell  from- 


Sprayed  half  . . 
Unsprayed  hal- 


Trees  tres 

ted 

Trees  treated 

with  Bordeaux 

with  sulphur 

mixture. (a) 

spray.  (6) 

Tree  No.— 

Tree  Xo.— 

1. 

2. 

3. 

4.          5. 

6. 

0 

4 

6 

18 

15 

15 

92 

92 

90 

85 

85 

85 

a  Foliage  estimated  May  18,  1S95. 


h  Foliage  estimated  May  10,  1S95. 


On  May  8  the  trees  were  examined,  and  the  notes  made  at  that  time 
state  that  the  sprayed  and  unsprayed  sides  presented  a  .striking  con- 
trast. It  is  said  that  "the  foliage  on  the  sprayed  half  of  the  trees  is 
perfection  itself  in  almo.st  all  cases.  It  is  very  dense  and  abundant, 
l)oth  below  on  the  limbs  and  above.  The  leaves  are  of  a  ver}'  dark, 
rich  green,  and  are  long,  soft,  and  beautiful.  The  growth  is  very 
thriftv,  in  fact,  unusually  so.  There  are  pro))ably  not  more  than  2  to 
;>  per  cent  of  the  leaves  curled  at  all  on  the  sprayed  half,  and  these  are 
confined  to  points  at  the  top  of  the  branches  not  properly  sprayed. 
On  the  unsprayed  half  of  these  trees  there  is  very  little  healthy  growth. 
Probably  95  per  cent  of  the  leaves  are  curled,  and  most  of  them  badly 
curled  and  distorted.  Probably  not  less  than  90  per  cent  of  those 
produced  thus  far  this  spring  will  drop.  The  color  of  the  foliage  is 
yellow  and  sickly.  Such  leaves  as  are  not  curled  are  small  and  light 
in  color.     The  foliage  upon  both  lower  and  upper  limbs  is  badly  affected. 


124 


PEACH    LEAF    CURL:    ITS    TSTATURE    AND    TREATMENT. 


What  little  growth  there  is  which  is  thus  far  free  from  curl  is  termi- 
nal— very  little  healthy  or  comparatively  healthy  growth  is  seen  from 
lateral  buds.  As  to  fruit,  I  may  say  that  much  is  dropping  from  the 
curled  side  and  little  from  the  other."     (Pis.  XYI  and  XYII.) 

The  work  of  thinning  the  fruit  from  the  sprayed  halves  of  these 
trees  was  not  conducted  at  the  time  the  sprayed  trees  of  the  general 
experiment  block  were  thinned.  The  writer  believes  that  the  records 
of  the  fruit  thinned  from  these  trees  were  not  kept  except  for  one  tree 
sprayed  on  one  side  with  Bordeaux  mixture.  The  fruit  on  the  sprayed 
half  of  this  tree  was  thinned  May  8,  1895,  and  amounted  to  1,145 
peaches,  which  weighed  23  pounds,  or  very  nearly  50  peaches  to  the 
pound.  These  peaches  were  very  uniform  in  size  and  stuck  tightly  to 
the  limbs.  If  they  could  have  grown  to  the  usual  size  when  picked 
in  the  fall  they  would  have  given  381  pounds  of  fruit.  No  peaches 
were  thinned  from  the  unsprayed  half  of  this  tree. 

The  yield  of  the  6  trees  was  carefully  determined  by  weighing  and 
counting  the  fruit  from  the  sprayed  and  unsprayed  sides  of  each  tree 
separately.     The  results  of  this  work  are  shown  in  the  following  table: 


Table  33. — Yield  of  sprayed  and  wisprayed  halves  of  trees. 


Bordeaux  mixture, 
tree  No. — 


Sulphur  sprav,  tree 
No.—  ■ 


Pounds  of  fruit  gathered  from — 

Sprayed  half 

Unsprayed  half 

Number  of  peaches  gathered  from 

Sprayed  half , 

Unsprayed  half 


2.S4.S 
14.3 


361. 6 
50.6 


1,064 
147 


286.  T 
25.3 


836 
74 


112.2 
48.6 


303 
132 


189.3 
80.4 


450 

220 


64.6 
35.3 


172 
94 


By  the  preceding  table  it  is  shown  that  the  sprayed  half  of  tree  1 
bore  718  peaches,  weighing  284.8  pounds,  while  the  unsprayed  half 
bore  onl}"  40  peaches,  weighing-  14.3  pounds.  In  this  case,  as  in  the 
case  of  the  other  trees  of  this  series,  the  localized  position  and  action 
of  the  fungus  of  curl  upon  a  tree  is  shown.  The  unsprayed  half  of 
the  tree  suffered  so  severely  from  the  disease  that  it  lost  92  per  cent 
of  its  foliage  and  all  but  14.3  pounds  of  fruit.  This  severe  attack 
on  one  side  of  the  tree  appeared  to  have  no  influence  whatever  over 
the  sprayed  limbs  of  the  other  side,  as  the  fruit  on  the  spraved  half 
was  thinned  of  1,145  peaches,  lost  but  2  per  cent  of  its  foliage,  and 
bore  284.8  pounds  of  as  fine  peaches  as  any  in  the  orchard.  On  the 
other  hand,  the  full  and  healthy  covering  of  foliage  on  the  sprayed  side 
of  the  tree  appears  to  have  had  no  beneficial  influence  over  the  diseased 
side.  Had  it  had  any  well-marked  beneficial  influence  the  fruit  of  the 
unsprayed  half  would  have  been  retained,  which  was  not  the  case. 
The  same  local  action  of  the  disease,  and  the  same  local  nourishing 
influence  due  to  the  assimilative  action  of  the  healthy  foliage  may  be 


DKSCKirTION  OF  PLATK   XVTI. 

This  plate  shows  the  condition  of  one  of  the  treeH  sprayed  on  one  side  at  the  time 
of  pii-king  the  fruit.  The  leaves  have  been  cut  away  with  pruning  shears  to  enal)le 
the  photograph  to  show  the  fruit  upon  the  sprayed  half  (right  side)  of  the  tree,  and 
the  absence  of  fruit  upon  the  unsprayed  half  (left  side) .  The  sprayed  half  matured 
284.8  pounds  of  the  finest  peaches;  the  unsprayed  half  matured  only  14.3  pounds. 
Over  1,100  peaches  were  thinned  from  the  sprayed  half  of  this  tree  to  enable  the 
limbs  to  l)ear  the  crop,  while  the  unsprayed  half  was  nnthinned  except  by  curl. 
(For  rei'ords  of  this  and  other  trees  sprayed  on  one  side  see  Chapter  YI,  also  comi)are 
with  Pis.  XYI,  XVIII,  and  XIX.) 


DESCRIPTION  OF  PLATE  XVITI. 

Peaches  gatheredjrom  the  tree  sprayed  oudnc  side  shown  in  the  precedmg  plate. 
The  fruit  shown  on  the  two  dryingltraysat  the  h'ft,  together  with  that  in  the  lower 
conipartment  of  the  tray  at  the  right,  was  gathered  from  the  sprayed  half  of  this  tree. 
Tlie  peaches  shown  in  the  uj>per  right-hand  eonqiartinent  were  all  that  mature^  on 
the  unsprayed  half  of  the  same  tree.  The  s])rayed  half  bore  718  peaches,  weigliiiig 
2S4.S  ])ounds;  the  nnsprayed  half  hore  only  40  peaches,  weighing"  1-J. 8  i)OUiids. 
(Compare  with  Pis.  XAT,  XVn,  and  XTX.)  '  ■-— — —  - 


Bull.  20,  Div.  Veg.  Phys,  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XVIII. 


>v/^^^\>'^vV 


-^    i-  <, 


1^     <     k. 


'.^:-:v-.,-!  ,\\'j: 0    ■  1- 


DESCKIPTION  OF  PLATE  XTX. 

This  is  a  photograph  of  a  hmb  of  the  sprayed  haU'  of  the  tree  shown  in  Pis.  XVI 
and  XVII,  after  the  removal  of  the  leaves  with  pruning  shears.  A  good  idea  of  the 
size  and  perfection  of  this  fruit  may  be  obtained  from  the  plate.  The  color  was 
strikingly  high  and  rich.  The  size  of  the  fruit  is  further  shown  by  the  fact  that  the 
l)eaches  averaged  252  per  100  pounds.  (See  note  on  this  work  at  the  close  of  Chap- 
ter VI,  p.  122;  also  refer  to  Pis.  XVI,  XVII,  and  XVIII.) 


Bull.  20,  Div.  Veg.  Phys    &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XIX. 


LOCAL    ACTION    OF    CURL    ON    FOLIAGE    AND    FRUIT.  125 

seen  in  the  condition  of  the  foliage  and  crop  on  the  sprayed  and 
nnsprayed  sides  of  the  other  trees  inchided  in  these  experiments. 

It  even  appears  likely,  both  from  observation  of  the  trees  and  from 
the  general  laws  of  use  and  disuse  and  supply  and  growth,  that  the 
influence  of  the  sprayed  upon  the  unsprayod  ix)rtions  of  the  tree,  in 
the  presence  of  an  attack  of  curl,  is  detrimental  rather  than  ])eneiicial. 
It  is  probable  that  the  half  of  the  tree  in  full  foliage,  instead  of  lend- 
ing material  aid  to  the  defoliated  side,  tends  to  further  rob  that  side, 
at  least  of  the  crude  sap  coming  from  the  roots. 

For  the  purpose  of  showing  the  reader  the  striking  results  obtained 
from  these  trees,  several  photographs  were  made  at  the  time  the  crop 
was  matured.  In  order  that  the  fruit  might  be  seen  upon  the  tree 
the  foliage  was  carefully  cut  away  and  a  screen  placed  behind  the 
tree  (PI.  XVII).  A  single  limb  was  also  photographed,  as  shown  in 
PI.  XIX.  The  fruit  gathered  from  the  sprayed  and  unsprayed  halves 
of  tree  1  is  likewise  shown  in  PI.  XVIII.  The  unusual  size  and 
brightness  of  color  of  the  fruit  from  the  sprayed  half  of  this  tree  was 
very  marked.  The  peaches  averaged  252  per  100  pounds.  The  aver- 
age of  peaches  for  the  large  experiment  block  was,  as  before  stated, 
299  per  100  pounds.  There  was  thus  a  gain  of  18.66  per  cent  in  size 
of  fruit  on  the  sprayed  half  of  this  tree  over  the  average  for  the  block. 


CHAPTER  VII. 

PREVENTIVE    SPRAY    WORK    CONDUCTED    BY    ORCHARDISTS. 
GENERAL   CONSIDERATION    OF   THE    AUXILIARY    WORK. 

While  planning  the  experiments  already  detailed  it  seemed  desirable 
to  set  on  foot  a  similar  line  of  work  among  peach  orchardists  in  gen- 
eral. It  was  thought  that  several  advantages  could  be  attained  from 
such  auxiliary  and  coincident  work:  (1)  It  would  indicate  the  effective 
ness  or  noneff'ectiveness  of  the  sprays  recommended,  in  controlling  curl 
under  the  various  conditions  of  variety,  situation,  soil,  temperature, 
atmospheric  humidity,  seasonal  variations,  etc.,  existing  in  the  many 
peach-growing  sections  of  the  country.  (2)  It  would  eliminate  the 
personal  element  of  the  other  experiments  being  conducted,  and 
would  introduce  various  new  conditions  of  orchard  work,  thus  point- 
ing out  the  efficiency  or  needs  of  the  general  grower  and  indicating 
what  features  of  the  work  should  receive  special  attention  in  offering 
final  recommendations.  (3)  It  would  introduce  the  methods  of  treat- 
ment in  many  peach-growing  centers,  and  by  means  of  the  object 
lessons  thus  set  up,  it  would  effect  a  much  more  rapid  and  general 
adoption  of  such  spra34ng  methods  than  could  be  hoped  for  otherwise. 

In  advance  of  the  inauguration  of  this  work,  which  was  begun  in 
the  fall  of  1893,  correspondence  was  opened  with  over  1,600  peach 
growers  in  all  peach-growing  centers  of  the  United  States.  To  each 
of  these  growers  was  sent  a  circular  describing  the  nature  and  cause 
of  peach  leaf  curl,  outlining  a  series  of  spraying  tests  which  it  was 
desirable  to  have  conducted  for  its  prevention,  and  supplying  the 
spraj^  formulae  known  to  have  given  good  results  in  California.  Each 
grower  was  given  the  facts  necessary  to  enable  him  to  carry  out  the 
work,  and  was  requested  to  furnish  the  Department  with  the  results  of 
his  experiments. 

A  very  large  number  of  growers  expressed  their  willingness  and 
desire  to  assist  in  conducting  these  experiments,  and  a  very  consider- 
able number  have  done  so  in  many  of  the  peach-grovring  centers.  It 
ma.j  also  be  said  that  the  number  of  growers  who  have  adopted  annual 
spraying  methods  as  a  result  of  this  introductory  experimental  work 
is  large  and  is  constantly  increasing.  In  fact,  the  spraying  of  peach 
trees  for  curl  has  become  very  general  in  many  of  the  peach-growing 
centers  of  the  United  States  where  the  disease  prevails. 
126 


AUXILIARY    WORK.  127 

Of  the  reports  which  have  been  received  of  work  conducted  by  the 
growers,  it  is  thought  best  to  inchide  a  few  from  those  regions  where 
curl  is  most  common.  The  reports  given  are  of  nuich  vakie,  and  in 
numerous  cases  they  show  that  the  experiments  were  carefully  carried 
out.  Representative  reports  will  l)e  given  from  the  lake  shore  fruit 
belt  of  Michigan,  from  the  Willamette  Valley,  Oregon,  where  peach 
culture  has  been  greatly  checked  by  curl,  and  from  several  growers  in 
California  and  elsewhere.  An  effort  has  ])een  made  to  present  these 
reports,  which  have  been  carefully  tal)ulated,  in  as  compact  form  as 
possible. 

NOTES    ox    THE    AUXILIARY    EXPERIMENTS    IN    MICHIGAN. 

A  very  considerable  number  of  peach  growers  in  the  more  northern 
portion  of  the  Michigan  fruit  belt  received  from  the  Department  a 
request  to  undertake  spraying  experiments  in  the  winter  of  1893-94 
for  the  prevention  of  peach  leaf  curl.  Among  these  orchardists  was 
Mr.  Smith  Hawle}',  of  Ludington.  This  gentleman,  as  well  as  several 
other  growers  of  Mason  and  Oceana  counties,  entered  heartily  into 
the  work,  the  result  being  that  at  present  a  veiy  large  number  of 
orchardists  are  annually  spraying  for  curl  in  that  region.  The  work 
conducted  by  Mr.  Hawley  involved  the  testing  of  a  number  of  spraJ^s 
in  early  and  late  winter  with  one  and  two  applications.  It  was  very 
carefully  carried  out,  and  as  the  disease  developed  quite  seriously  in 
that  region  in  the  spring  of  1894  his  results  are  most  interesting  and 
valuable.  The  data  supplied  by  his  report  are  presented  in  the  fol- 
lowing table  and  notes: 


128 


PEACH    LEAF    CURL*.    ITS    NATURE    AND   TREATMENT. 


•saajj  paXBidsnii 


■saaji  paABJdg 


fig's 


■saajj  paA-Bjdsu.i 


0=10         o 


•S99JJ  paXBjdg 


•Sai.iBJds  puooas 


•SniiBjds  JSJIJ 


■paABadsuii 


•paiiBadg 


la 
^>■. 


CO 


g'53 


0 

0  f- 

is 

iso 

OJ 

03  ^ 

0 

ow 

g-sa- 


!s.5  5-S^  fe  OS  o-s  a  &  t- 

^  C.  ^-  -^  m       t-        o  .S  "^  <1> 


P.«. 


0.5 


vC.  O -. 

1— 'COr^--OiOiCTr'^'M 


,  cj  ^  —  ~'  —  -^  >:? 


^  tn  o  5  ■*  ■^-  ;S  K  ^  K  ;S  K  ^  o  .S  ^ 


lO»0'^'-HCOrHy^^C<)r-l  CO  iClO  "V 


•^catauadxa  jo  ■o^^ 
paB  Bihnuo}  jo  lajjai 


^O)       ^    CO  t^ 


^,03 


AUXILIARY    WORK.  129 

TIk^  prcH'odinj^  t{il)le  o-ivo.s  the  details  of  eij^ht  of  Mr.  Hawley's 
cxpcrinnMits.  The  oxpci'lnioiits  arc  distiiij>-uished  by  MUin])er.s  (1-8), 
and  tlio  formula'  usihI  hy  letters  (A,  B,  and  C).  Mr.  Hawley's  notes 
on  these  experiments  were  written  chiefly  on  two  dates,  the  first 
imnuMliately  after  the  estimates  of  foliao-e  wei-e  mad(>  and  the  second 
shortly  after  the  fruit  was  gathered.  His  statements  in  general  are 
yiven  in  the  foUowino-  notes: 

Experiment  i: 

June  23,  1894. — Tliis  experiment  was  made  under  rather  unfavorable  circnm- 
stam'es,  as  the  wind  came  up  quite  strong  after  I  had  commenced,  and  consequently 
I  could  not  do  the  work  as  thoroughly  as  I  wished,  but  the  results  now  promi.se  to 
be  entirely  satisfactory.  The  foliage  is  perfectly  fresh  and  green,  and  apparently  the 
peaches  are  going  to  hang  on.  Another  thing  that  now  appears  to  be  well  estab- 
lished is  that  the  earlier  spraying  is  the  better.  [See  notes  under  experiment  2.] 
There  is  now  (juite  a  perceptible  difference  to  be  noticed  between  early  and  late 
spraying  as  regards  the  foliage. 

October'],  189-1:. — This  experiment  has  demonstrated  the  effectiveness  of  the  spray 
used.  While  the  crop  was  not  large,  owing  to  the  unhealthy  state  of  the  trees 
from  leaf  curl  last  year,  yet  it  was  about  three  times  as  lavge  on  the  sprayed  as  on 
the  unsprayed  trees.  The  fruit  was  much  nicer.  I  could  easily  pick  out  the  baskets 
of  fruit  from  the  sprayed  trees. 

Experiment  2: 

June  2,3,  1894. — This  experiment  has  given  entire  satisfaction  so  far,  as  the  foliage 
of  the  trees  is  perfect  and  the  fruit  is  hanging  on  well.  This  experiment,  taken  in 
(H)nnection  with  the  others,  indicates  that  the  blue  vitriol  solution,  C,  acts  quicker 
than  the  sulphur  solution.  The  winter  sprayings  seem  fully  as  effective  with  the  sul- 
phur solution  as  with  the  blue  vitriol, but  the  spring  spraying  is  not  (juite  as  good. 

October!,  1894. — While  the  difference  in  the  amount  of  fruit  gathered  from  the 
sprayed  and  unsprayed  trees  is  not  as  great  as  in  some  of  the  other  experiments,  j'et 
the  effect  is  fully  as  apparent,  for  these  trees  were  not  nearly  as  badly  affected  last 
year  as  some  others,  and  consequently  they  all  had  a  fair  load  of  fruit.  There  was  a 
far  greater  difference  noted  in  the  foliage  than  in  the  fruit. 

Experiment  S: 

The  first  spraying  of  this  experiment  was  on  January  19,  and  was  followed  by  a 
heavy  rain  storm,  which  lasted  twenty-ff>ur  hours,  and  will  undoubtedly  prevent  the 
full  benefit  of  the  work  from  being  realized,  but  the  work  was  very  thoroughly  done 
and  may  be  effective. 

June  23,  1894. — The  second  spraying  was  well  done,  and  at  this  date  the  effect 
.«eems  to  show  (1)  that  formula  B  is  not  strong  enough  to  have  the  desired  effect; 
and  (2)  that  two  sprayings  are  not  much  better  than  one,  provided  the  work  is 
thoroughly  done  with  one  spraying,  and  provided,  aLso,  the  spraying  is  followed  by 
good  weather. 

.October  1,  1894. — This  experiment  has  given  greater  satisfactif»n  than  anticipated. 
The  proportion  of  sprayed  to  unsprayed  fruit  is  better  than  expected  at  the  time  of 
the  estimate  on  the  loss  of  foliage. 

Experiment  4-' 

June  23,  1894. — The  contrast  between  the  sprayed  and  unsprayed  trees  at  tliis  date 
is  very  decided  in  this  experiment.     The  first  s})raying  was  on  the  .«ame  date  as 
experiment  3,  and  followed  by  rain.     The  last  was  done  April  12  with  formula  C, 
and  was  well  done,  and  the  trees  now  look  fine. 
19093— No.  20 9 


130  PEA.CH    LEAF    CUEL:    ITS    NATURE    AND   TREATMENT. 

October  1,  1894. — The  results  of  this  experiment  are  rather  disappointing,  as  I  was 
led  to  believe  when  I  made  the  estimate  of  the  loss  of  foliage  in  June  that  the  results 
would  be  more  satisfactorj'  than  with  experiment  3.  Whether  the  solutions  used 
had  the  effect  of  neutralizing  each  other,  or  whether  formula  B,  having  Ijeen  first 
applied,  prevented  any  benefit  from  formula  C,  I  can  not  tell. 

Experiment  5: 

June  23, 1894. — The  first  spraying  of  this  lot  w^as  followed  by  ten  hours'  rain,  the  last 
spraying  by  good  weather.  The  treated  trees  present  a  fine  appearance,  but  the  con- 
trast is  not  so  great  as  in  some  other  experiments,  for  the  control  trees  are  an  outside 
row  and  apparently  not  as  badly  affected  as  those  farther  in  the  orchard.  I  do  not 
anticipate  a  very  large  difference  in  the  fruit  yield. 

October  1,  1894. — This  experiment  has  turned  out  just  as  I  thought  it  would.  The 
difference  in  the  amount  of  fruit  from  the  sprayed  and  unsprayed  trees  is  not  great, 
yet  it  is  quite  satisfactory  considering  the  conditions. 

Experiment  6: 

June  23,  1894. — This  experiment  was  thoroughly  made,  but  was  unfortunately 
followed  by  twenty-four  hours  of  w'arm  rain,  commencing  ten  hours  after  the  spray- 
ing, so  that  the  result  is  not  as  satisfactory  as  desired,  but  the  effect  is  so  noticeable 
that  the  difference  can  be  seen  half  a  mile  away. 

October  1,  1894. — The  results  of  this  experiment  are  entirely  satisfactory.  In  spite 
of  the  fact  that  the  spraying  was  followed  by  rain  and  then  by  very  cold  weather, 
the  yield  of  fruit  was  one-third  more  on  the  treated  trees  than  on  the  untreated  trees, 
but  what  pleases  me  most  is  the  very  great  difference  in  appearance  of  the  trees  now. 
Those  that  were  treated  have  made  double  the  growth  this  season  that  the  untreated 
hrees  have.  They  are  holding  their  leaves  late  and  have  twice  the  buds  set  for  another 
year,  and  are  fresher  and  healthier  in  every  way. 

Experiment  7: 

June  23,  1894. — The  result  of  this  experiment  thus  far  seems  to  show  that  the 
formula  used  is  not  strong  enough  to  accomplish  the  work  desired.  There  is  at  this 
date  less  difference  to  be  noted  between  the  treated  and  untreated  trees  than  in  any 
other  experiment. 

October  1,  1894. — This  experiment  has  resulted  about  as  I  thought  it  would,  from 
the  appearance  of  the  trees  in  June.     I  do  not  think  formula  B  is  strong  enough. 

Experiment  8: 

Jime  23,  1894. — I  regard  this  as  one  of  the  most  valuable  experiments  in  the  series. 
It  has  so  far  shown  the  best  results.  The  imtreated  trees  look  as  though  a  blight  had 
struck  them,  appearing  at  this  date  as  if  they  were  going  to  die,  while  the  sprayed 
trees  look  as  fresh  and  healthy  as  young  trees  that  never  had  any  disease.  One 
curious  thing  I  have  noticed  is  in  relation  to  a  branch  from  one  of  the  untreated  trees 
which  reaches  across  to  one  of  the  treated  ones.  This  l)ranch,  of  course,  got  sprayed 
when  the  tree  was  sprayed  with  which  it  mingles,  and  it  is  as  full  of  leaves  and  fruit 
as  the  treated  tree,  while  the  balance  of  the  tree  to  which  it  belongs  is  bare  of  leaves 
and  fruit. 

October  1,  1894. — The  final  results  of  this  experiment  have  proved  w^hat  I  expected. 
There  is  a  greater  difference  in  yield  than  in  any  other  experiment,  while  the  differ- 
ence in  appearance  between  the  treated  and  untreated  trees  is  yet  very  marked.  The 
treated  trees  look  as  fresh  and  healthy  as  young  trees,  while  the  others  still  look 
very  bad.  These  trees  have  always  been  very  heavy  bearers,  and  consequently  have 
not  attained  a  very  large  size.  They  were  never  very  badly  affected  by  leaf  curl  till 
this  year. 


AUXILIARY    WORK. 


131 


In  the  eight  experiinont.s  described  by  Mr.  Hawley  the  percentages 
of  not  gain  in  fruit  of  the  sprayed  trees  over  the  unsprayed  wore  as 
follows: 

Tablk  35. — I'erccntages  of  net  gain  in  fruit  shown  in  eight  spraying  experiments  conduded 
by  Mr.  Smith  Hawley,  of  Ludington,  Mich. 


Experiment  No. 

Formula. a 

Net  gain. 

Pa-  cent. 
191 

46 
174 

41 

Experiment  No. 

Formula. 

Net  gain. 

1 

A 

5. 

(; 

Per  cent. 
35 

') 

C 

6 

A 

49 

3 

B 

B  and  C . . 

7 

B 

21 

4 

8 

C 

1,424 

a  See  table  34.  ' 

Owing  to  the  fact  that  Mr.  Hawley's  experiments  were  conducted 
with  different  varieties  of  peach,  an  accurate  comparison  can  not  be 
instituted  between  them.  From  the  very  excellent  results  obtained  in 
experiment  8,  where  the  unsprayed  trees  lost  90  per  cent  of  their 
leaves  and  the  sprayed  trees  only  3  per  cent,  and  where  the  net  gain 
in  fruit  by  the  sprayed  trees  was  1,424  per  cent  of  the  yield  of  the 
unsprayed  trees,  the  writer  believes  Mr.  Hawley's  conclusions  are 
correct,  viz,  that  the  spray  used  in  this  experiment  gave  the  best 
results.  That  the  ^;ame  spray  did  not  give  equalh^  striking  contrasts 
in  experiments  2,  4,  and  5  is  probably  due  mainly  to  the  fact  that 
the  trees  of  these  experiments  were  not  of  the  same  variety  as  those 
of  experiment  8,  but  were  much  more  resistant  to  disease,  hence  no 
spray  could  have  produced  in  the  former  experiments  the  .same  con- 
trast between  sprayed  and  misprayed  trees.  That  the  trees  of  experi- 
ments 2,  4,  and  5  were  not  as  badly  diseased  as  those  of  experiment  8 
is  shown  to  be  a  fact,  for  the  unsprayed  trees  of  the  latter  experiment 
lost  00  per  cent  of  their  leaves  from  curl,  while  those  of  the  former 
experiments  lost  only  .50  per  cent.  The  same  evidence  is  given  by  the 
fruit.  The  un.sprayed  trees  of  experiment  8  bore  only  3.7  pounds  of 
fruit  per  tree,  while  the  unsprayed  trees  of  experiments  2,  4,  and  5 
averaged  45. T,  11.6,  and  ^2.4  pounds  of  fruit  per  tree,  respectiveh'. 

From  the  preceding  facts  it  appears  that  the  most  active  and  satis- 
factory spray  used  })y  ]\Ir.  Hawley  was  that  containing  a  pounds  of 
copper  sulphate,  5  pounds  of  (piickliuie,'  and  45  gallons  of  water.  This 
is  e.specially  interesting  from  the  fact  that  this  spray  also  gave  the 
best  results  among  the  35  fornmlse  tested  by  the  writer  in  the  Sacra- 
mento Valley. 

The  relative  value  of  the  stronger  sulphur  spray  (formula  A)  and  the 
Bordeaux  mixture  used  ))v  Mr.  Hawley  (formula C)  is  well  Itrought  out 
in  an  experiment  conducted  I)}'  him  on  a  somewhat  similar  scale,  but 
with  a  single  variety  of  peach — Hills  Chile.  This  experiment  admits 
of  very  satisfactory  comparisons  being  drawn,  and  is  summarized  in 
the  foUowiuof  table: 


132 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


Table  36. — Experiment  No.  9,  conducted  by  Mr.  Smith  Hawley. 


Row 

No. 

Formula 
used. 

Variety  of  trees. 

Age  of 
trees. 

Num- 
ber of 
trees. 

Date  of  spraying. 

Total 

yield  of 

fruit. 

Net  gain  of 
fruit  over 
yield  of  un- 
sprayed 
trees. 

1 

A 

Hills  Chile 

i'ears. 
5 
5 
5 
5 

6 
6 
6 
6 

April  12 

Pounds. 
270 
63 
306 
189 

Per  cent. 
328 

2 

do 

Unsprayed 

February  8 

January  19 

3 

c 

do 

354 

4 

A 

do 

V     200 

The  preceding  experiment  shows  that  Mr.  Hawley  obtained  from 
his  Hills  Chile  trees  a  net  gain  in  fruit  of  354  per  cent  b}^  spraying 
with  the  Bordeaux  mixture  (formula  (y),  and  a  net  gain  of  328  per 
cent  with  the  stronger  sulphur  spray  when  applied  on  April  12  and 
200  per  cent  when  applied  on  January  19.  These  results  indicate  that 
the  early  winter  treatment  will  probably  not  prove  as  effective  in 
Michigan  as  a  treatment  of  the  trees  shortly  before  the  buds  swell  in 
the  spring.  It  is  probable,  however,  that  the  copper  sprays  will  act 
more  quickly  than  the  sulphur  sprays,  on  which  account  the  latter 
should  be  allowed  somewhat  more  time  for  action  than  the  copper 
sprays,  by  applying  them  a  little  earlier  in  the  spring.  The  copper 
sprays  may  be  applied  until  the  lirst  buds  begin  to  open,  if  neces- 
sary, but  such  a  late  application  of  the  sidphur  sprays  would  endanger 
the  buds  and  new  growth. 

The  following  are  Mr.  Hawley's  notes  on  this  experiment : 

Experiment  P.- 
June 23,  1894. — This  experiment,  although  on  a  small  scale,  has  lieen  very  inter- 
sting  and  instructive,  and  has  been  noted  and  admired  by  all  who  saw  it.  The 
rees  stand  on  a  slope,  and  a  person  standing  on  the  opposite  slope,'  only  a  few  rods 
away,  can  see  every  tree,  and  the  best  possible  chance  is  had  to  observe  the  effect  of 
the  different  sprays,  and  to  compare  the  treated  with  the  untreated  trees.  The  con- 
trast at  this  time  is  very  remarkable.  The  trees  were  quite  badly  affected  by  leaf 
curl  last  year. 

October  1,  1894. — The  contrast  between  the  treated  and  untreated  trees  is  very 
great  as  regards  yield  of  fruit,  and  the  contrast  in  the  trees  themselves  at  this  date  is 
quite  as  remarkable.  The  treated  trees  look  fresh  and  healthy  and  have  made  a  fine 
growth,  while  the  untreated  trees  look  sickly  and  have  made  very  little  growth, 
looking,  in  fact,  a  year  or  two  younger,  as  regards  size,  than  the  others. 

Late  in  the  season  of  1894  Mr.  Hawley  tested  the  sulphur  and  copper 
sprays  to  ascertain  the  comparative  action  of  the  same  upon  buds 
which  were  considerably  swollen.  He  learned  that  the  sulphur  spraj^ 
injured  the  buds  to  such  an  extent  as  to  reduce  the  yield,  while  it 
prevented  curl.  The  copper  spray,  however,  prevented  curl  and  gave 
a  decided  increase  in  yield.  He  thus  reaches  the  conclusion  that 
formula  A  is  more  injurious  to  buds  than  formula  C.  While  this  is 
true  if  the  spray  is  applied  at  too  late  a  date,  it  ma}'  be  safely  applied 
at  an  earlier  date.     It  should  also  be  mentioned  that  the  .sulphur  sprays 


AUXILIARY    WORK. 


133 


have  insecticidal  properties  much  :superior  to  those  of  the  copper 
sprays. 

The  DepartiiuMit  work  condueted  by  Mr.  Ilawley  seems  to  haveclearly 
demonstrated  the  possibility  of  controlling-  the  most  severe  attacks  of 
curl  in  the  lake  shore  region  of  Michigan  with  a  single  spraying,  when 
this  is  done  thoroughly  and  at  the  proper  time.  In  experiment  8  the 
untreated  trees  were  so  badly  ali'ected  that,  as  already  stated,  90  per 
cent  of  the  foliage  and  all  but  3.7  pounds  of  the  fruit  fell  from  the  trees, 
])ut  ])v  spraying  similar  trees  Mr.  Ha wlev  saved  all  but  3  per  cent  of  the 
lea\es-^a  gain  of  2,1>00  per  cent  of  foliage — besides  increasing  the  yield 
of  fruit  1,424  per  cent.  In  other  words,  the  sprayed  trees  held  30 
times  as  much  spring  foliage  and  over  15  times  as  much  fruit  as  the 
unspr^iyed  trees  at  their  side,  all  being  of  the  same  variet}'. 

In  the  southern  portion  of  the  Michigan  frjuit  belt  a  number  of 
growers  assisted  the  Department  in  conducting  experiments.  Among 
the  reports  received  from  that  section  is  one  by  Mr.  George  Lannin, 
of  South  Haven.  Mr.  Lanuin's  work  is  summarized  in  the  following 
table : 


T.\HLE  o7. — Experimental  work  conducted  by  Mr.  George  Lannin,  of  South  Ifaven,  Midi., 
in  the  spring  and  mmnicr  of  1895. 

[Nature  of  soil,  sandy.] 


Formulae  for 

•lo  gallons  of 

water. 

Variety  of  trees. 

Age 

of 

trees. 

Number 
of 

trees— 

Date  of— 

Percentage 
of  leaves 
lost  by— 

Date 
when 
loss  of 
leaves 
was 
esti- 
mated. 

Fruit 

produced 

by- 

a  V 
o 

¥ 

First 
spray- 
ing. 

Second 
spray- 
ing. 

o 

g 

P.    - 

CO 

i 

-a 

s 

& 
a 

i 

0) 

u 

ci' 
ft 

1 

OS 

p. 
a 

t3 

1 

(E) 
2 

{F) 
3 

(G) 
4 

flO    lbs.     sul- 
I  phur,  20  lbs. 
1  lime,  5  lbs. 
{  salt. 

5  llxs.  copper 
sulphate,  10 
lbs.  lime. 

(2  lbs.  copper 
1  sulphate,    :? 
1  pt.s.    ammo- 
1  nia. 

[5  oz.   copper 
1  carbonate,  3 
I  pts.    ammo 
l  nia. 

^Barnard  

Hills  Chile 

VHales  Early 

>Crawfords  \jite. 

Years. 

0 
6 
6 
6 

10 
10 
10 
10 

10 
10 
10 
10 

Apr.  10 
...do.. 
...do.. 
...do.. 

.May  17 
June 25 
...do.. 
June  8 

20 
15 
20 
10 

40 
35 
40 
30 

July  10 
...do.. 
...do.. 
...do.. 

Lbs. 
1,200 

1,300 

1,760 

1,800 

Lbs. 
830 

GOO 

680 

700 

The  spray  formulse  tested  by  Mr.  Lannin  were  not  included  in  the 
work  of  Mr.  Hawlev,  and  are  therefore  characterized  as  Formulae  D, 
E,  F.  and  G.  As  Mr.  Lannin  sprayed  difierent  varieties  of  peach  trees 
with  4  formulte,  the  experiments  can  not  ])e  compared  with  one  another 


134 


PEACH  LEAF  OUKL*.  ITS  NATURE  AND    TREATMENT. 


to  advantage.  The  value  of  all  the  sprays  used  is  shown,  however, 
by  the  gain  in  fruit  obtained.  The  percentage  of  net  gain  in  fruit 
was  44,  116,  158,  and  157  per  cent,  respectively.  These  figures  show 
that  the  eau  celeste  (Formula  F)  and  the  ammoniacal  copper  carbonate 
(Formula  G)  gave  satisfactory  results.  The  action  of  the  disease  on 
the  foliage  of  the  trees  of  experiment  3  was  more  severe  than  it  was  on 
the  foliage  of  the  trees  of  experiment  4.  The  unsprayed  trees  of  the 
former  experiment  lost  10  per  cent  more  of  their  leaves  than  the  trees 
of  the  latter.  The  percentage  of  gain  in  fruit  from  the  sprayed  trees 
of  experiment  3  was,  however,  fully  as  great  as  that  from  the  sprayed 
trees  of  experiment  4.  This  shows  that  the  eau  celeste  (Formula  F) 
was  more  effective  in  combating  the  disease  than  the  ammoniacal  copper 
carbonate,  which  was  applied  in  experiment  4. 

Mr.  F.  N.  Chesebro,  of  South  Haven,  sprayed  19  Crawfords  Late 
and  19  Oldmixon  trees  in  the  spring  of  1894,  leaving  19  trees  of  each 
variety  for  comparison.  The  formula  used  was  15  pounds  of  sulphur, 
30  pounds  of  lime,  and  10  pounds  of  salt  to  60  gallons  of  water.  Mr. 
Chesebro  did  not  report  the  exact  yield  of  his  trees,  but  stated  that 
the  sprayed  trees  lost  20  per  cent  of  their  foliage  and  the  unsprayed 
trees  80  per  cent — a  saving  of  60  per  cent  of  the  foliage  by  a  single 
spraying.     His  report  is  as  follows: 

Table  38. — Experimental  ivork  conducted  by  Mr.  F.  N.   Chesebro,  of  South' Haven,  Mich., 

in  the  spring  of  1894- 

[Variety  of  trees,  Crawfords  Late  and  Oldmixon  Cling;  nature  of  soil,  sandy  loam.] 


Number  of 

Per  cent  of 

^ 

trees— 

^ 

leaves  lost  by— 

a 

Date 

. 

when 

Formula. 

i 

'6 

to 

P. 

0) 

<u 

loss  of 

leavos 

was  esti- 

O 

d 

0 

bo 

•A 

P. 

"0 

0) 

P. 
0 

mated. 

'A 

< 

03 

t3 

Q 

m 

t3 

Years. 

("1.5  lbs.  sulphur 

1 

J30  lbs.  lime 

1    '' 

38 

38 

Mar.     7 

20 

80 

)  10  lbs.  salt 

1.60  gal,  water 

Mr.  J.  F.  Taylor,  of  Douglas,  Mich.,  reported  favorably  upon  the 
spray  work  conducted  by  him  in  1894.  He  used  three  different  sprays, 
treating  50  trees  with  each,  and  leaving  a  like  number  unsprayed 
for  comparison.  The  formulte  used  were  those  designated  as  A,  B,  and 
C,  in  the  spray  work  of  Mr.  Smith  Hawley.  Mr.  Taylor  says,  in  regard 
to  his  work: 

The  blossom  buds  had  swollen  somewhat  when  I  began  spraymg,  but  the  leaf  buds 
were  quite  dormant.  Formula  A  was  used  on  March  29,  Formula  B  on  April  6,  and 
Formula  C  on  April  20.  Blossoms  began  to  open  on  the  last  days  of  April,  and  by 
the  6th  of  May  trees  were  well  covered  with  bloom.    The  trees  sprayed  were  6  years 


AUXILIARY    WORK.  135 

old,  and  of  the  following  varieties:  St.  John,  Barnards  Early,  Hinman,  Switzerland, 
Gold  Drop,  and  Early  Freestone.  Some  of  these  varietie.s  cnrled  very  badly  last 
year,  especially  Early  Freestone.  The  soil  is  quite  uniformly  a  gravelly  loam,  with 
clay  siilisdil  undrr  all  varieties.  I  niatle  only  one  applieation  with  each  formula.  I 
think  two  applieations  would  have  been  better.  I  sprayed  50  trees  and  then  omitted 
50  in  each  plat,  or  with  each  foruuila.  I  think  Fornuila  0  gave  as  good  ri'sulta  as 
any  of  them.' 

After  the  trees  were  in  full  h^af  I  invited  neighboring  fruit  men  to  go  through  the 
orchard  and  note  the  conditions  of  the  trees  sprayed  and  vmsprayed.  They  found 
the  foliage  of  trees  that  had  been  sprayed  almost  free  from  curl,  while  the  vmsprayed 
trees  were  badly  curled.  *  *  *  The  unsprayed  trees  had  a  larger  percentage 
of  small  dead  limbs  through  the  top  than  those  that  were  sprayed,  and  the  prospect 
for  future  iTops  is  therefore  better  where  the  trees  were  sprayed.  *  *  *  i  hope  to 
follow  the  work  up  more  (ixtensively  next  spring,  and  will  begm  the  work  earlier  in 
the  season,  if  necessary.  If  Formula  C  will  continue  to  give  as  good  results  as  it  did 
last  spring,  I  prefer  to  use  it. 

Mr.  S.  I.  Bates,  of  Shelby,  Mich.,  sprayed  a  few  Stump  the  World 
trees  in  the  spring  of  18JU,  leaving  an  equal  number  unsprayed  for 
comparison.  The  crop  from  the  sprayed  trees  was  double  that  fl'om 
the  unsprayed  trees  at  their  side,  and  a  large  percentage  of  the  foliage 
was  also  saved.  Mr.  Bates  states  that  the  spray  seems  to  put  new  life 
and  vigor  into  the  trees,  especially  young  trees.  With  respect  to  the 
action  of  curl  on  old  trees,  he  writes  that  there  is  an  old  orchard  just 
across  the  road  from  his  own  which  has  had  curl  until  the  trees  have 
no  V)earing  wood  left  except  at  the  extreme  tops,  and  the  owner  ' "  does 
nothing  to  prevent  the  disease  and  gets  but  little  fruit.  "^ 

NOTES   ON    THE    AUXILIARY    EXPERIMENTS   IN    OREGON. 

The  climatic  conditions  under  which  peach  culture  is  pursued  in  Ore- 
gon and  Washington  vary  greatly.  At  the  east  of  the  Cascade 
Mountains  the  conditions  approximate  in  many  districts  those  pre- 
vailing in  much  of  California.  At  the  west  of  this  range  local 
intiuences  determine  the  greater  or  less  adaptation  of  each  valley  or 
region  to  the  cultivation  of  the  peach.  Generalh'  speaking,  however, 
the  humidity  of  the  atmosphere  for  a  major  portion  of  the  year  is 
much  in  excess  of  that  prevailing  generally  at  the  east  of  the  Cas- 
cades or  in  California.  Iii  this  respect  also  this  northwest  region 
is  quite  distinct  from  the  conditions  met  with  in  most  of  the  peach- 
growing  regions  of  the  East.  In  fact  the  climate  of  western  Oregon 
and  Washington  is  such  as  to  call  for  separate  consideration  in  connec- 
tion with  our  present  work.     For  this  reason  special  eti'ort  has  been 

^This  is  the  same  formula  that  was  found  very  satisfactory  by  Mr.  Smith  Hawley, 
at  Ludington,  Mich.,  and  by  the  writer  in  the  Sacramento  Valley. 

''  There  are  thousands  of  such  peach  orchards  in  the  peach  districts  of  the  United 
States.  To  those  Avho  are  interested  in  the  renewal  of  young  and  Ijearing  wood  uijon 
lower  limbs  and  upon  old  trees,  the  writer  would  refer  to  the  data  ])resented  in  Chap- 
ter V  of  this  bulletin,  where  the  influence  of  sprays  on  the  vegetation  of  trees  has 
been  quite  fully  considered. 


136    PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

made  to  carry  out  spra^'ing  experiments  in  western  Oregon,  so  that 
the  needs  of  the  growers  west  of  the  Cascades  could  be  supplied. 

The  great  rainfall  which  annually  occurs  on  the  west  side  of  the 
Cascade  Mountains  makes  the  vegetation  of  that  region  especially 
liable  to  fungous  diseases,  and  the  peach  is  no  exception  to  this  rule. 
In  the  Willamette  Valley.  Oregon,  along  the  lower  Columbia,  and  in 
the  basin  of  Puget  Sound  in  Washington,  peach  leaf  curl  has  become 
a  great  hindrance  to  extensive  peach  culture.  In  view  of  these  facts, 
many  peach  growers  of  Oregon  and  Washington  were  requested  by 
the  Department  to  conduct  experiments  for  the  control  of  the  disease, 
and  it  was  taken  up  by  a  number  in  1894  and  again  in  1895.  Several 
of  the  gentlemen  who  conducted  such  work  prepared  reports  of  the 
same,  which  should  prove  of  much  interest  and  value  to  the  peach 
growers  of  both  States. 

Among  those  who  entered  heartily  into  the  work  was  Mr.  M.  O. 
Lownsdale,  of  Lafa^^ette,  Oreg.  This  gentleman  conducted  verv 
extensive  spraying  tests  according  to  plans  supplied  bv  the  Depart- 
ment, both  in  189-1  and  1895,  using  in  his  work  as  many  as  30  acres  of 
young  peach  trees  in  1894.  At  the  close  of  his  experimental  spray 
work  Mr.  Lownsdale  gave  the  following  general  facts  respecting  the 
situation  in  the  Willamette  Valley,  in  which  Lafayette  is  situated, 
being  the  center  of  an  extensive  fruit-growing  region  of  Yamhill 
County : 

I  hand  you  herewith  my  report  of  experiments  for  the  prevention  of  peacli  leaf 
curl  for  the  season  of  1895,  to  which  I  desire  to  add  a  few  words  upon  the  status  of 
tlie  peach  industry  in  the  Northwest. 

Peach  growing  has  been  abandoned  to  a  great  extent  in  the  "Willamette  Valley 
because  of  the  attacks  of  the  shot-hole  fungus  and  leaf  curl.  Growers  have,  not 
understood  the  causes  of  their  troubles,  and  have  attributed  them  to  peculiar  climatic 
conditions,  or  have  groiiped  them  under  the  indefinite  term  blight;  but  now  that  the 
nature  of  these  fungous  troubles  is  better  imderstood,  and  the  remedies  suggested 
have  proved  so  efficacious,  it  seems  that  the  abandonment  of  the  industry  may  have 
been  premature.  The  success  of  the  preliminary  experiments  has  restored  the  con- 
fidence of  orchardist.s  in  a  great  measure,  and  as  it  becomes  widely  known  that  our 
fungous  troubles  can  be  controlled,  increased  attention  will  be  given  to  peach 
growing. 

Experiments  through  a  series  of  four  years  on  a  block  of  6  acres  of  Early  Char- 
lotte peaches  indicate  that  it  may  be  possible  to  prevent  these  destructive  fungi 
from  getting  a  foothold  in  an  orchard.  This  block  of  trees,  which  was  i)lanted  in 
dormant  bud,  has  received  an  annual  treatment  in  October  and  two  treatments  each 
spring  with  the  ammoniacal  copper  carbonate,  with  the  exception  of  the  spring  of 
1895,  when  your  modified  Bordeaux  was  applied.  Neither  leaf  curl  nor  shot-hole 
fungus  has  develoj^ed  in  this  block.  A  fair  crop  of  fruit  was  harvested  this  summer — 
the  fourth  from  the  bud — and  the  trees  are  healthy  and  have  grown  luxuriantly.  If 
intending  planters  would  select  perfectly  .healthy  trees — either  yearling  or  dormant 
buds — and  would  give  them  one  treatment  in  autumn,  as  the  Department  has  sug- 
gested, in  addition  to  the  spring  treatment  for  leaf  curl,  it  is  probable  that  peach 
growing  would  again  become  profitable  in  the  Willamette  Valley.  I  am  convinced 
that  if  the  efficacy  of  the  modified  Bordeaux  mixture  for  the  contrtd  of  leaf  curl 
h  id  been  known  five  years  ago  the  industry  would  have  been  flourishing  to-day,  for 


AUXILIARY    WORK.  187 

with  the  treatment  for  leaf  curl,  whicli  adds  &o  much  vigor  and  sturdinosf^  to  the  tree, 
as  indicated  by  the  pushing  out  of  dormant  buds  on  lower  Ijranchcs,  the  liability  to 
attacks  of  other  fungi  would  have  been  lessened,  and  it  would  then  have  been  dilH- 
cult  for  the  great  shot-hole  wave  to  sweep  over  our  orchards  as  it  did  in  1893  and 
1894. 

The  ([uality  of  peaches  grown  in  the  Willamette  Valley  is  unsurpassed.  No 
locality  in  the  United  States  can  produce  more  delicious  fruit.  It  seems  judicious, 
then,  to  attempt  to  save  this  industry  and  render  it  i)rolita])le  again.  To  this  end  it 
is  to  be  hoped  that  the  Department's  methods  for  the  prevention  of  these  fungous 
attacks  will  be  widely  adopted. 

The  .spray  work  conducted  by  Mr.  Lownsdale  in  the  spring  of  1894 
involved  the  spraying  of  some  1,700  young  trees  and  the  testing  of 
10  spray  formuhe.  With  each  of  the  10  experiments  was  included 
a  considerable  number  of  unsprayed  trees  left  for  comparison,  these 
control  trees  being  of  the  same  variety  as  the  trees  spraved  in  the 
same  experiment,  and  in  each  case  they  were  so  located  at  the  sides  or 
among  the  spraA^ed  trees  as  to  admit  of  just  comparison.  Mr.  Lowns- 
dale's  report  upon  this  extensive  work  is  given  below.  All  the  spray 
formula?  prepared  by  him  were  for  45  gallons  of  water: 

Thirty  acres  of  peach  trees  were  devoted  to  experimental  work  under  your  direc- 
tion. These  trees  were  Crawfords  Early  and  Early  Charlotte  (a  seedling  from  the 
Crawfords  Early) .  In  addition  to  these  tests  10  acres  were  left  wholly  untreated 
as  a  block  check  against  the  mam  experiments.  All  these  trees  were  3  years  old, 
and  had  curled  so  badly  m  1893  that  they  had  twisted  into  shapeless  maisses,  though 
they  had  partially  recovered  later  in  the  season.  The  general  plan  of  work  was  to 
treat  a  block  of  at  least  100  trees  with  each  formula,  leaving  intervening  check  rows 
untreated.  In  some  instances  check  rows  were  interspersed  through  the  treated 
block,  it  being  desirable  to  have  all  conditions  as  nearly  alike  as  possible. 

Formula  A  (10  pounds  sulphur,  20  pounds  lime,  10  pounds  salt)  was  applied  March 
21,  1894,  to  264  trees  in  8  rows,  with  2  control  rows  on  each  side  of  the  l)lock.  Curl 
appeared  in  about  3  per  cent  of  the  foliage  of  the  sprayed  trees,  while  60  per  cent  of 
the  foliage  of  the  untreated  controls  was  affected. 

Formula  B  (5  pounds  sulphur,  10  pomids  lime,  5  pounds  salt)  was  applied  IMarch 
23  to  204  trees  in  4  rows,  with  2  check  rows  on  each  side  of  block.  About  3  per 
cent  of  foliage  was  affected,  while  untreated  check  rows  curled  very  badly. 

Formula  C  (5  poimds  sulphur,  10  pomids  lime)  was  applied  to  166  trees  on  March 
22  in  a  block  4  rows  wide,  with  the  customary  2  check  rows.  Curl  developed  on 
about  10  j)er  cent  of  the  foliage  of  the  treated  trees,  and  upon  about  60  per  cent  of 
that  of  the  controls. 

Fornmla  G  (6  pounds  copper  sulphate,  10  pounds  lime)  was  applied  to  42  trees 
on  March  17.  About  5  per  cent  of  foliage  was  affected  on  tlie  sprayed  trees,  but  the 
controls  were  so  badly  affected  that  they  scarcely  survived  the  sunmier. 

Formula  II  (3  pounds  copper  sulphate,  5  pounds  lime)  was  applied  March  20  to 
186  trees  in  a  block  6  rows  wide.  About  8  per  cent  of  the  foliage  of  the  sprayed 
trees  was  affected,  while  the  controls  were  as  under  Formula  G. 

Fornmla  I  (2  pounds  copper  sulphate,  3  pints  26°  ammonia)  was  applied  March  20 
to  26  trees  with  26  check  trees.  About  5  per  cent  of  curl  developed  on  treated  trees, 
while-the  check  row  was  very  badly  injured. 

Formula  J  (4  pounds  copper  sulphate,  5  pounds  sal  soda,  3  pints  26°  ammonia)  was 
ai>i)lied  March  20  to  2(5  trees,  with  2  check  rows  of  26  trees.  Curl  developed  on  3 
per  cent  of  the  foliage  of  the  treated  trees,  but  the  controla  were  almost  destroyed. 


138  PEACH    LEAF    CURL:    ITS    NATURE    AND    TREATMENT. 

Formula  K  (5  pounds  sulphur,  15  pounds  lime)  Mas  applied  March  19  to  278  trees 
in  a  block  10  rows  wide,  with  control  rows  of  69  trees  each  on  each  side.  Curl 
appeared  on  about  2  per  cent  of  the  foliage  of  the  treated  trees,  while  the  check  rows 
were,  as  in  the  previous  year,  a  mass  of  curled  leaves  and  twisted  branches.  Formula 
K  was  also  applied  to  25  Salway  trees  and  to  15  Alexanders,  which  had  curled  very 
badly  for  many  years,  the  Salways  always  being  defoliated  completely.  These  trees 
were  8  years  old.     No  curl  appeared  on  either  variety. 

Formula  L  (5  pounds  copper  sulphate,  15  pounds  lime)  was  applied  March  13  and 
again  March  21  to  262  trees,  with  7  check  rows  interspersed  through  the  l)lock.  Less 
than  one-fourth  of  1  per  cent  of  curl  appeared  on  the  treated  trees  of  this  test,  while 
the  check  rows  were  almost  destroyed  by  the  disease.  The  greater  portion  of  these 
imtreated  trees  have  been  dug  up  and  replaced  (February  13,  1895) .  Treated  trees 
in  this  block  made  an  excellent  growth,  though  cultivated  only  moderately,  and  a 
great  majority  were  absolutely  free  from  curl. 

The  ammoniacal  copper  carbonate.  Formula  M  (5  ounces  copper  carbonate,  3  jjuats 
26°  ammonia)  ^  was  applied  March  22  to  210  trees,  2  check  rows  of  69  trees  being  left 
alongside.  Less  than  3  per  cent  of  curl  appeared  on  the  block,  while  65  per  cent  of 
the  foliage  of  the  control  trees  was  curled.  This  formula  was  also  applied  twice,  at 
intervals  of  two  weeks,  upon  5  acres  of  trees  upon  which  no  curl  could  be  found. 
This  experiment,  though  remarkably  successful,  was  not  as  conclusive  as  desired,  as 
no  control  trees  were  left.  This  was  upon  a  block  of  thrifty  trees,  of  which  I  did 
not  care  to  sacrifice  any  portion  to  an  experiment.  The  same  treatment  had  pre- 
served them  the  previous  year,  and  I  feared  a  change. 

All  my  treated  trees  have  grown  satisfactorily  this  year,  but  the  10-acre  check 
block  of  imtreated  trees  was  so  nearly  destroyed  by  curl  that  all  the  trees  will  be 
dug  up.  Several  hundred  are  dead,  and  of  the  remainder  I  think  no  tree  has  had  a 
growth  of  12  inches. 

It  will  be  seen  from  Mr.  Lownsdale's  report  of  the  work  in  1894 
that  several  of  the  sprays  used  gave  most  excellent  results.  On  May 
18  of  that  year  he  wrote: 

Curl  has  developed  moderately,  and  everywhere  the  better  condition  of  treated 
over  untreated  trees  is  apparent.  The  trees  treated  with  5  pounds  of  copper  sul- 
phate and  15  pounds  of  lime  may  be  said  to  be  absolutely  free  from  the  curl  and  the 
experiment  a  success.  This  block  was  sprayed  twice  in  March.  The  check  rows  in 
this  block  and  alongside  are  curled  as  badly  as  any  trees  except  seedlings. 

The  modified  eau  celeste  (Formula  J)  is  also  giving  good  results,  as  is  the  5  pounds 
of  sulphur  and  15  pounds  of  lime;  but  I  believe  the  copper  sulphate,  5-pound  for- 
mula, is  in  the  lead.  This  may  be  attributed  to  more  thorough  work,  as  most  of  the 
other  sprays  were  only  applied  once. 

Owing  to  the  fact  that  no  fruit  records  could  be  obtained  from  Mr. 
Lownsdale's  experiments  in  1894,  as  the  trees  were  yet  too  small, 
arrangements  were  made  for  the  testing  of  some  of  the  more  valuable 
sprays  in  the  spring  of  1895.  The  experiments  of  1895  show  the  gain 
in  both  foliage  and  fruit,  though  the  jdeld  was  low,  resulting  from  the 
use  of  5  sprays — 1  sulphur  and  4  copper.  The  experiments  were  con- 
fined to  the  Crawf ords  Early  variety,  and  in  each  experiment  the  trees 
received  two  sprayings  in  March.  All  trees  were  4  years  old,  but 
rather  small.  Mr.  Lownsdale's  data  on  this  work  are  presented  in 
the  following  table: 


AUXILIARY    WORK. 


139 


Tabi>k  39. — Experimental  work  conducted  hy  Mr.  M.  0.  Lownsdale,  of  Lafaydte,  Orey., 
in  the  spring  and  summer  of  1895. 

[Variety  of  trees,  Crawfords  Early;  nature  of  soil,  red  hill.] 


F o r mu  1  re  for  '15 
gallons  of  water. 


110  lbs.  sulphur 

•JO  lbs.  lime 

[ft  lbs.  stilt 

15  lbs.  copper  sul- 
l)hate 

llO  lbs.  lime 

[2  lbs.  copper  sul- 
phate   

[3  pts.  ammonia 

15  oz.  copper  car- 
bonate   

[3  pt-s.  ammonia... 

(5  lbs.  copper  sul- 
phate   

15  lbs.  lime 


Number 

of 

trees. 

Date  of— 

Leaves  lost 
by- 

Fruit  pro- 
duced by— 

Age 

of 

trees. 

Date 
when  I0.SS 
of 
leaves 
was  esti- 
mated. 

■i 

First 
spray- 

Second 
spray- 

i 
i 

>. 
"  a; 

0 

ft2 

0, 

ing. 

ing. 

M*^ 

C 

t3 

P.  ■ 
m 

el 

t3 

a, 

Yrs. 

Per  ct. 

Per  ct. 

IJlK. 

Lbs. 

\      ^ 

8() 

91 

Mar.     7 

Mar.  27 

10 

35 

June  18 

340 

187 

f      ** 
f      ^ 

110 
110 

CS 

87 

....do... 

....do... 

5 
0 

35 
30 

....do... 
....do... 

480 
807 

62 

Mar.     9 

....do... 

193 

1   ' 

2ti8 

07 

Mar.     8 

Mar.  28 

Tr  i  - 
fling. 

30 

....do... 

1,204 

h 

189 

91 

Mar.    9 

....do... 

None  . 

40 

....do... 

1,048 

15 

But  few  comments  upon  the  preceding  table  are  required.  It  makes 
the  fact  perfectly  evident  that  two  spring  sprayings  are  sufficient  to 
almost  absolutely  control  leaf  curl  in  the  Willamette  Vallej'.  In  a 
letter  written  June  25,  1895,  Mr.  Lownsdale  says: 

Peach  leaf  curl  has  not  developed  a.s  badly  in  this  section  as  it  did  last  year.  I 
have  estimated  that  about  40  per  cent  appeared  on  most  of  my  control  trees.  Two 
sprays  with  lime,  10  and  15  pounds,  and  copper  sulphate,  5  pounds,  were  an  abso- 
lute success.  Lime  in  the  amount  of  15  pounds  gives  the  best  results,  there  being  100 
per  cent  of  healthy  foliage  on  trees  sprayed  with  this  amount  and  5  pounds  of  cop- 
per sulphate.  Practically  the  same  results  were  obtained  with  two  applications  of 
the  ammoniacal  copper  carbonate.  It  is  impossible  to  find  a  curled  leaf  on  acres  and 
acres  of  treated  trees. 

In  the  Rogue  River  Valley,  in  the  southern  tier  of  counties  of  Oregon, 
the  conditions  are  somewhat  more  fayorable  for  peach  culture  than  in 
much  of  the  Willamette  Valley.  The  climate  is  somewhat  intermedi- 
ate in  charactei"  between  that  of  northwestern  Oregon  and  northern 
California.  Peach  culture  is  quite  extensive  about  Ashland,  Medford, 
etc.  The  reports  of  Air.  E.  F.  Meissner,  of  Kerby,  Josephine  County, 
and  of  Mr.  N.  S.  Bennett,  of  Medford,  Jackson  County,  are  fairly  rep- 
resentative of  those  received  from  experiments  conducted  in  southern 
Oregon.  Mr.  Aleissner's  report  again  shows  the  great  effectiveness  of  5 
pounds  of  copper  sulphate,  10  pounds  of  lime,  and  45  gallons  of  water. 
With  this  formula  he  sprayed  4  Salway  trees  4  years  old,  leavingan  equal 
number  unsprayed  for  comparison.  Two  treatments  were  given,  the 
first  February  22,  the  second  March  10,  1895.  From  the  sprayed 
trees  10  per  cent  of  the  foliage  was  lost  from  curl,  while  from  the 


140  PEACH    LEAF    CURL  I    ITS    NATURE    AND    TREATMENT. 

unsprayed  trees  90  per  cent  was  lost,  leaving  the  trees  nearh^  bare. 
Unfortunately,  frost  killed  the  buds,  and  no  comparison  of  fruit  was 
possible,  but  it  is  safe  to  say  that  the  fall  of  90  per  cent  of  the  leaves 
would  have  caused  the  loss  of  the  crop,  while  10  per  cent  loss  would 
have  occasioned  little,  if  any,  falling  of  fruit.  Mr.  Meissner  writes 
respecting  his  work  that  the  copper  sulphate  spray  "has  given  far 
better  results  than  the  sulphur,  lime,  and  salt,"  and  that  "the  trees 
sprayed  with  the  bluestone  mixture  look  the  best  of  any  in  the 
orchard. " 

Mr.  Bennett  used  the  5-pound  formula  for  the  Bordeaux  mixture 
as  given  for  Mr.  Meissner,  He  sprayed  but  once,  on  March  11, 1895. 
The  29  trees  sprayed  averaged  41  pounds  of  fruit  per  tree,  while  the 
single  control  tree  jdelded  but  9  pounds,  or  a  net  gain  in  fruit  of  388 
per  cent.  The  fact  of  most  interest  in  connection  with  this  work  is, 
however,  that  the  variety  treated  was  the  Elberta,  which  is  probably 
more  universally  susceptible  to  leaf  curl  than  any  other  variety  now 
grown  in  the  United  States.  The  control  of  curl  on  this  variety  was 
almost  absolute,  as  will  be  seen  from  the  following  letter  from  Mr. 
Bennett: 

I  send  you  to-day  a  report  of  the  spraying  for  leaf  curl.  The  experiment  was  an 
honest  trial,  and  I  feel  very  jubilant  over  the  success.  I  have  reported  only  the 
Elberta  variety,  as  it  was  one  of  that  kind  which  I  left  unsprayed.  I  am  more  than 
pleased  with  the  results,  and  can  say  that  a  good  trial  is  all  that  any  man  needs  who 
has  the  welfare  of  his  orchard  at  heart  (his  pocketbook  as  well) .  The  peaches  from 
the  sjirayed  trees  were  first-class,  clean,  and  sold  at  the  highest  market  price.  I 
notice  a  very  marked  difference  in  the  general  health  of  the  trees  in  favor  of  those 
sprayed.  The  leaves  lost  by  the  sprayed  trees  were,  perhajis,  one-half  of  1  per  cent. 
The  unsprayed  tree  was  a  little  above  an  average  tree  in  the  spring.  There  were  29 
sprayed  trees,  which  yielded  an  average  of  44  pounds  of  choice  fruit  to  the  tree, 
nearly  half  of  which  packed  56  peaches  to  the  box.  I  sprayed  75  Wheatland  trees 
with  the  same  success  as  far  as  leaf  curl  is  concerned.  They  are  fine,  healthy  trees 
now,  and  bore  a  good  crop  this  season.  They  have  been  bad  about  curling,  but  I 
left  an  Elberta  because  that  variety  is  the  worst  to  curl,  and  if  spraying  did  them  no 
good  I  intended  to  grub  them  out. 

Mr.  P.  W.  Olwell,  of  Centralpoint,  Oreg.,  applied  the  sulphur 
spray  to  400  Muir  trees  in  his  orchard,  leaving  25  trees  unsprayed  for 
comparison.  The  formula  used  by  Mr.  Olwell  was  15  pounds  of  sulphur, 
30  pounds  of  lime,  and  10  pounds  of  salt  to  60  gallons  of  water.  His 
trees  were  5  years  old,  growing  in  black,  loamy  soil.  They  were 
sprayed  March  10.  The  sprayed  trees  did  not  lose  any  foliage  from 
disease,  while  the  control  trees  lost  25  per  cent.  The  fruit  records 
were  not  reported. 

NOTES   ON   THE    AUXILL^RY   EXPERIMENTS   IN    CALIFORNIA, 

Besides  the  experimental  work  conducted  by  the  writer  in  the  Sac- 
ramento Valley  in  the  years  1894  and  1895,  a  considerable  number  of 
growers  assisted  in  carrying  on  experiments  in  different  portions  of 


AUXILIARY    WORK. 


141 


California.  Reports  have  been  riH'eivod  from  s(^veral  of  these  growers, 
and  while  in  some  instances  they  are  not  as  complete  as  desired,  the 
results  shown  are  amply  sufficient  to  determine  the  practical  value  of 
the  work  undertaken. 

Among-  the  more  complete  and  carefully  prepared  reports  is  one 
from  Mr.  A.  D.  Cutts,  of  Live  Oak,  Sutter  County.  The  work  was 
carried  out  in  the  Avintei"  of  185*2-1>8,  and  was  one  of  the  experiments 
which  led  to  the  writer's  detailed  series  of  experiments  outlined  in  the 
present  bulletin.  In  this  orchard  the  spray  was  not  used  in  1898  for  the 
control  of  leaf  curl,  but  was  applied  for  the  purpose  of  destroying-  the 
San  Jose  scale,  which  was  gaining-  a  foothold  in  the  orchard.  The 
trees  infested  by  scale  were  scattered  through  a  40-acre  block  of  the 
Crawfords  Late  variety.  These  trees  had  been  marked,  and  in  Febru- 
ar}^,  1898,  were  thoroughly  sprayed  with  the  sulphur  spray,  consist- 
ing of  15  pounds  sulphur,  30  pounds  lime,  10  pounds  salt,  and  60  gal- 
lons water.  Only  a  few  of  the  trees  were  entirely  sprayed.  As  curl 
developed  seriously  in  that  region  in  the  spring  of  1893,  the  contrast 
between  the  scattered  sprayed  trees  and  the  remainder  of  the  block 
was  very  striking,  and  Mr.  Cutts  kindly  consented  to  preserve  the 
records  of  yield  of  a  few  of  the  sprayed  and  unsprayed  trees  for  use 
in  this  connection.  In  the  table  which  follows  is  shown  the  amount 
of  fruit  produced  by  each  of  the  9  sprayed  trees  included  in  Mr. 
Cutts's  records,  as  well  as  the  weight  and  number  of  first,  second,  and 
third  quality  peaches.  The  same  facts  are  given  for  an  equal  num- 
ber of  neighboring  unsprayed  trees  for  comparison. 

Tablk  40. — Experimental  work,  conducted  hy  Mr.  A.  D.  Cutts,  of  Live  Oak,  Cal.,  in  the 

sjmng  and  summer  of  1893. 

[Cra^yfords  Late,  4  years  old.] 


Sprayed  trees. 

Unsprayed  trees. 

Total  pounds  of— 

Number  of— 

Total  pounds  of— 

Number  of— 

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25 
17 
34 
12 
15 

17 
7 
6 
9 
6 

20 
5 
5 

735 
615 
385 
605 
668 
815 
148 
367 

126 
110 

70 
138 

86 
151 

60 

65 

130 
45 
54 
60 
32 

139 
30 
27 

2 

1 

2 

1 

4 
3 

3 

4 

5 

2 

2 

5 

6 

7 

1 
3 

8 

...... 

1 
3 

3 

8 

8 

9 

18 

Total. 

1,497 

1,218 

196 

83 

4,514 

902 

646 

68 

31 

21 

6 

120 

79 

56 

The  average  yield  of  fruit  of  the  sprayed  trees  given  in  the  table 
was  166.22  pounds  per  tree,  while  the  average  yield  of  the  unsprayed 
trees  was  but  6.4ri:  pounds.     This  rcjorcsents  a  gain  in  fruit  bv  the 


142    PEACH  LEAF  CURL!  ITS  NATURE  AND  TREATMENT. 

sprayed  trees  above  the  yield  of  the  unspra>'ed  trees  of  24.8  times  the 
yield  of  the  latter.  In  other  words,  there  was  a  gain  in  yield  of  2,481 
per  cent  from  spraying.  Much  valuable  information  was  also  supplied 
by  Mr.  Cutts  in  relation  to  the  preparation  and  application  of  sprays, 
and  the  writer  has  considered  these  subjects  in  other  portions  of  the 
bulletin.  Some  of  the  more  striking  photographs  of  sprayed  and 
unsprayed  trees  have  also  been  obtained  from  Mr.  Cutts's  orchard, 
as  well  as  the  records  of  fruit  buds  elsewhere  discussed  (Pis.  VII 
and  XX). 

The  report  of  a  test  of  the  Bordeaux  mixture  (5  pounds  copper 
sulphate,  10  pounds  lime,  and  45  gallons  water)  was  furnished  b}^  Mr. 
H.  B.  Gaylord,  of  Auburn,  Placer  County.  This  experiment  was 
made  in  the  spring  of  1895.  Mr.  Gaylord  sprayed  10  Heaths  Cling 
peach  trees  and  4  nectarine  trees,  the  variety  of  which  was  not  stated. 
The  spraying  was  done  February  15.  Mr.  Gaylord  states  that  the 
unsprayed  nectarines  curled  so  badly  that  they  bore  no  fruit  at  all, 
while  the  4  sprayed  trees  yielded  320  pounds.  He  says  that  every 
alternate  tree  was  sprayed  in  a  row  of  nectarines,  and  that  the  sprayed 
peach  trees  were  in  the  worst  places  in  the  orchard.  Respecting  the 
result  of  the  work  Mr.  Gaylord  writes,  in  part: 

I  herewith  send  you  a  partial  report  on  the  experiment  for  leaf  curl.  I  used  only 
one  formula.  The  result  is  perfectly  satisfactory.  I  sprayed  some  peach  and  some 
nectarine  trees,  both  with  good  results.  One  nectarine  tree  sprayed  has  not  a  curled 
leaf,  while  one  of  the  same  kind,  about  15  feet  from  it,  which  was  not  sprayed,  has 
lost  nearly  all  its  leaves.  The  contrast  is  so  great  that  it  would  be  wortli  while  to 
have  them  photographed.  A  neighbor,  Mr.  G.  P.  Dixon,  used  formula  3  (2  pounds 
copper  sulphate,  3  pints  ammonia,  and  45  gallons  water)  with  the  same  results,  so 
that  I  am  satisfied  that  the  copper  sulphate  is  what  does  the  work. 

Mr.  Gaylord  also  states  that  no  leaves  were  lost  from  the  peach  trees 
sprayed,  while  all  of  the  leaves  curled  on  the  unsprayed  trees  of  the 
remainder  of  the  orchard. 

In  Amador  County  an  extensive  experiment  was  made  in  the  spring 
of  1895,  by  Mr.  George  Woolsey,  of  lone.  Mr.  Woolsey  sprayed  some 
2,500  trees  of  various  varieties  of  peach  and  nectarine  with  5  pounds  of 
copper  sulphate,  10  pounds  of  lime,  and  45  gallons  of  water,  and  left 
720  trees  unspra3^cd  for  comparison.  The  spraying  was  done  from 
Februarj'^  20  to  March  10.  Most  of  the  sprayed  trees  lost  no  foliage, 
but  a  few  in  a  wet  situation  lost  not  to  exceed  25  per  cent,  while  the 
unsprayed  trees  lost  not  less  than  50  per  cent  of  the  leaves  and  a  large 
amount  of  fruit. 

Mr.  Woolsey  gives  some  notes  respecting  the  work  in  the  spring  of 
1895,  as  follows: 

A  block  of  about  200  trees,  Salways  12  to  15  years  old,  on  well-drained  soil,  and 
500  Salways  4  years  old,  adjoining,  I  did  not  spray,  thinking  they  were  curl  proof. 
I  regret  I  did  not  spray  them.  *  *  *  Tlie  leaves  are  dropping,  as  well  as  a  large 
percentage  of  the  fruit.     I  shall  certainly  spray  them  in  the  future.     *    *    *    The 


DESCRIPTION  OF  PLATE  XX. 

Sprayed  and  unsprayed  Crawfords  Late  trees  in  the  orchard  of  Mr.  A.  D.  Cutts, 
Live  Oak.  The  tree  at  the  right  was  sprayed  in  February,  1893,  with  Ume,  sulphur, 
and  salt;  the  trees  at  the  left  were  untreated.  See  "Notes  on  auxiliary  experi- 
ments in  California,"  for  a  full  account  of  the  work  at  Liveoak.  (Photographed 
in  May,  1893,  after  most  of  the  diseased  leaves  had  fallen  from  the  unsprayed  trees. 
Compare  with  PI.  VII.) 


Bull.  20,  Div.  Veg.  Phys.  &  Path.,  U.  S.  Dept  of  Agriculture. 


Plate  XX. 


».,..■,;,     ,  .v;,.r  ..'  fc-^- 


^i^T** ' 


f/  ■.  ... 


C^':r 


?&:L--.-»>>i*r^ 


AUXILIARY    WORK.  143 

apparent  result  of  Hprayinfj,  one  api)lication,  is  as  follows:  Four  control  trees  of  Early 
Rivers,  adjoining  trees  si)rayed  March  2,  are  badly  curled,  leaveH  dropi)ing,  and  also 
the  greater  portion  of  the  fruit.  The  adjoining  sprayed  trees  of  this  tender  variety 
are  all  right  (no  curl)  and  make  quite  a  marked  contrast.  Besides  these,  4  white 
nectarines  and  4  Bilyeau  peaclxes,  left  at  the  same  time,  show  curl  and  loss  of  fruit, 
although  not  as  badly  as  the  Early  Rivers.  The  surrounding  sprayed  trees  look 
vigorous  and  healthy,  with  no  curl. 

Mr.  Woolsey  was  among  the  first  pcacli  growers  to  adopt  the  copper 
sprays  for  the  control  of  curl.  His  first  experiments  were  made  in 
18J>2,  and  tliev  proved  so  satisfactory  that  he  sprayed  quite  (extensively 
in  1893  and  again  in  1894.  The  work  in  1893  was  of  special  interest, 
as  the  following  extract  from  a  conmmnication  received  from  liim  will 
show: 

I  sprayed  nearly  all  my  peach  and  apricot  trees.  I  say  nearly  all;  for,  time  jjress- 
ing,  I  found  I  would  not  get  over  all  the  peaches,  so  to  save  what  I  considered  the 
most  valuable  portion,  viz,  the  3'oung  lower  growth,  I  had  that  sprayed  and  left  the 
tops  unsprayed.  The  season  was  a  damp  one  and  leaf  curl  was  very  prevalent  with 
my  neighbors.  On  my  place  all  trees  sprayed  were  exempt,  all  others  badly  affected 
and  crops  on  them  almost  a  failure.  On  the  ones  partly  sprayed  there  was  a  healthy 
growth  on  the  lower  part  of  the  trees,  while  they  were  denuded  of  foliage  above. 

Mr.  Woolsey's  work  in  1894  was  negative,  owing  to  the  nondev^^lop- 
ment  of  the  disease  that  season. 

Two  peach  growers  of  Eldorado  County,  Mr.  John  M.  Da}^,  of 
Placendlle,  and  Mr.  A.  L.  Kramp,  of  Diamond  Spring,  furnished  the 
writer  with  reports  of  their  experiments  conducted  in  the  spring  and 
summer  of  1895.  Mr.  Day  tried  4  formuhe,  each  showing  a  decided 
saving  of  foliage,  but  the  fruit  was  lost  from  frost.  The  spray  used 
by  Mr.  Kramp  was  composed  of  10  pounds  sulphur,  20  pounds  lime,  5 
pounds  salt,  and  45  gallons  of  water.  He  sprayed  600  trees,  3  years  old, 
of  the  Hales  Early,  Briggs  Early,  and  Wilcox  Cling  varieties,  and  3,000 
unsprayed  trees  were  left  for  comparison.  Tlie  sprayed  trees  lost  no 
foliage  and  yielded  48,000  pounds  of  peaches,  while  the  unsprayed 
trees  lost  not  less  than  50  per  cent  of  their  leaves  and  yielded  00,000 
pounds.  The  average  yield  of  the  spra3'ed  trees  was  thus  80  pounds 
per  tree,  while  tlie  average  yield  of  the  unsprayed  trees  was  but  20 
pounds,  a  net  gain  of  300  per  cent. 

Gen.  N.  P.  Chipman,  of  Red  Blufl",  has  been  using  for  at  least  two 
years  a  formula  for  Bordeaux  mixture  which  gave  the  writer  exceed- 
ingly good  results  at  Biggs  (see  row  21  of  the  writer's  experiments, 
p.  117).  Mr.  Chipman  writes  that  his  experiments  were  upon  several 
varieties  of  peach  trees  and  that  excellent  results  were  obtained.  He 
further  says:  "1  used  equal  parts,  or  5  pounds  bluestone,  5  pounds 
quicklime,  and  45  gallons  water.  I  believe  you  have  found  an  infalli- 
ble remed3^  I  have  used  this  spray  two  years  with  good  effect."  Mr, 
Chipman  first  observed  the  effects  of  this  spray  in  the  experiment 
block  at  the  Rio  Bonito  orchard,  in  the  summer  of  1895. 


144  PEACH    LEAF    CURL:    ITS    NATURE    AND   TREATMENT. 

NOTES   ON   THE   AUXILIARY    EXPERIMENTS   IN   NEW   YORK,    INDIANA,  AND 
OTHER   PEACH-GROWING    STATES. 

Much  experiineiital  work  for  the  control  of  leaf  curl  has  l^een  under- 
taken at  the  suggestion  of  the  Department  b}^  the  peach  growers  of 
New  York,  Indiana,  Illinois,  Ohio,  Kentucky,  Maryland,  Pennsylva- 
nia, Georgia,  Tennessee,  North  Carolina,  Arkansas,  Missouri,  Kansas, 
and  other  peach-growing  States  not  already  considered  in  this  bulletin. 
For  instance,  SO  prominent  peach  growers  of  various  peach-growing 
centers  of  New  York  were  given  full  instructions  for  the  control  of 
curl  in  the  winters  of  1893-94  and  1891^95,  and  requested  to  report  their 
work,  which  in  a  number  of  instances  was  carefuUj^  done.  The  same 
is  true  of  54  growers  in  Ohio,  136  in  Pennsylvania,  etc.,  and  in  each 
case  where  the  work  was  properly  conducted  the  results  were  in  har- 
monj^  with  those  already  discussed  in  this  chapter.  For  this  reason, 
as  well  as  from  the  fact  that  the  work  already  considered  has  been 
selected  from  those  sections  of  the  country  which  are  fully  represen- 
tative of  the  different  climatic  conditions,  it  is  not  thought  necessary 
or  desirable  to  enter  much  further  into  the  details  of  the  work.  One 
or  two  experiments  may  be  mentioned,  however,  before  closing  the 
consideration  of  this  phase  of  the  subject. 

Mr.  Joseph  M.  Cravens,  of  Madison,  Ind.,  reported  almost  absolute 
success  in  the  control  of  curl  in  his  orchard.  The  sprayed  trees  of 
the  4  experiments  made  in  no  case  showed  more  than  3  per  cent  of 
curled  leaves,  while  the  amount  of  curl  on  the  foliage  of  the  unsprayed 
trees  ranged  from  25  to  45  per  cent.  Mr.  Cravens  states  in  a  letter 
accompanying  his  report  that  he  sprayed  separate  rows  through  his 
orchard  which  were  sufficiently  far  apart  not  to  have  the  spray  affect 
the  intervening  rows  even  if  the  wind  blew  at  the  time  of  application, 
and  further  that  he  is  satisfied  that  two  of  the  sprays  used  would  have 
given  absolute  results  had  they  been  applied  to  every  portion  of  every 
twig. 

Mr.  W.  T.  Mann,  of  Barkers,  N.  Y.,  sprayed  25  trees  with  the  lime, 
sulphur,  and  salt  spray  April  9,  1894,  and  left  25  trees  at  their  side 
without  spraying  for  comparsion.  On  May  28  only  42  diseased  leaves 
were  found  on  the  25  spraj^ed  trees,  while  as  high  as  40  per  cent  of 
curled  foliage  was  present  on  some  of  the  unsprayed  trees.  On  the 
same  date  as  the  other  spraying  was  done  25  trees  were  spmyed  with 
Bordeaux  mixture,  while  21  were  left  for  comparison.  By  May  28 
only  59  curled  leaves  had  developed  on  the  entire  25  sprayed  trees, 
while  of  the  21  unsprayed  trees  several  had  as  high  as  30  to  35  per  cent 
of  curled  leaves.  Mr.  Mann  says  that  from  the  fact  that  among  the 
50  trees  treated  not  one  showed  an  appreciable  amount  of  disease, 
while  all  through  the  orchard  trees  were  badly  affected,  was  to  him 
very  satisfactory  evidence  of  the  value  of  the  treatment,  especially  as 


AUXILIARY    WOKK.  145 

ho  did  not  undortako  tho  work  witli  any  oroat  doo-rcc  of  confidence  as 
to  .succe.s.sful  results. 

Mr.  James  A.  Staples,  of  Marlboro,  N.  Y.,  states  that  in  the  sea- 
sons of  1894,  18J>5,  and  18'JO  he  made  the  spray  tests  on  pcnu-h  trees 
for  leaf  curl  which  had  been  sugj^ested  l)y  the  writer,  and  says  he 
is  well  satisfied  that  the  disease  can  be  controlled  by  proper  spraying. 
He  states  that  the  winter  treatment  gave  him  the  best  results. 

Mr.  A.  D.  Tripp,  of  North  RidgeAvay,  N.  Y.,  states  in  his  report  of 
spra}^  work  for  curl  that  he  treated  208  trees  and  left  S'20  trees 
unsprayed.  From  the  sprayed  trees  he  gathered  "360  baskets  of  as  fine 
fruit  as  ever  went  to  market."  The  baskets  were  one-third  of  a  bushel, 
and  the  peaches  averaged  66  to  the  basket.  From  the  untreated  trees 
only  15  baskets  w^ere  gathered,  and  a  portion  of  this  fruit  was  imper- 
fect. The  variety  was  the  Elberta. 
19093— No^  20 10 


CHAPTER  VIII. 

PREPARATION,    COMPOSITION,    AND    GENERAL    CHARACTERS    OF 

THE  SPRAYS  USED. 

PREPARATION   OF   THE    COPPER   SPRAYS. 

It  is  not  the  intention  to  consider  in  this  place  the  many  forms  of 
copper  sprays  which  have  been  used  at  one  time  or  another  in  the 
treatment  of  fungous  diseases,  but  to  confine  the  discussion  to  those 
forms  tested  in  the  present  work. 

Most  of  the  formula?  for  those  copper  sprays  which  have  been  tested 
in  the  treatment  of  peach  leaf  curl  have  been  personally  prepared  at 
one  time  or  another  and  the  results  thev  gave  have  been  carefully 
studied.  Several  other  formulae  have  been  recommended  by  the  writer, 
but  these  were  prepared  and  applied  by  the  growers  themselves,  so 
that  for  the  results  of  this  work  their  reports  have  been  consulted. 
There  are  still  a  few  other  formula?  for  copper  sprays  which  have 
been  reported  upon,  but  these  are  the  suggestions  of  others  or  were 
chosen  by  the  growers  themselves. 

The  difierent  copper  sprays  which  have  been  tested  in  separate  form 
(not  in  union  with  other  fungicides)  are  shown  in  the  following  list. 
This  list  includes  22  distinct  formula?.  Each  formula  is  that  used  with 
45  gallons  of  water,  except  the  first  for  Bordeaux  mixture,  which  was 
with  48  gallons. 

Table  41. — Copper  sprays  applied  for  the  control  of  peach  leaf  curl. 

Copper  sulphate  solution: 

*  4  pounds  copper  sulphate,  45  gallons  water. 

*  2  pounds  copper  sulphate,  45  gallons  water. 
Bordeaux  mixture: 

t24  pounds  copper  sulphate,  45  pounds  lime. 
*6  poimds  copper  sulphate,  lo  pounds  lime. 
i  5  pounds  copper  sulphate,  15  pounds  lime. 
*.3  pounds  copper  sulphate,  15  pounds  lime. 
j  6  pounds  copper  sulphate,  10  pounds  lime. 

*  5  pounds  copper  sulphate,  10  pounds  lime. 

*  3  pounds  copper  sulphate,  10  pounds  lime. 

*  5  pounds  copper  sulphate,  5  pomids  lime. 

*  4  pomids  copper  sulphate,  5  pounds  lime. 
*3  pounds  copper  sulphate,  5  pounds  lime. 

*  Prepared  and  tested  by  the  writer,  and  in  many  cases  also  tested  ]jy  growers. 
t  Chosen  and  tested  by  grower. 

i  Recommended  by  the  writer,  but  tested  by  the  growers. 
146 


PREPAKATI  N  OF    THE  COPPER  SPRAYS.  147 

Bordeaux  mixture — Continued 

*2  pounds  foi)per  yulpliate,  5  pounds  lime. 

*(>  pounds  copper  sulphate,  4  pounds  lime. 

*()  pounds  copper  sulphate,  15  poun<ls  lime. 

*3  pounds  copper  sulphate,  2  pounds  lime. 
Eaa  celc^e: 

*  4  pounds  cojiper  sulphate,  8  pints  annnonia  (26°) . 

*2  pounds  copper  sulphate,  :>  pints  ammonia  (26°). 
Modified  cau  celeste: 

*4  jKHinds  copper  sulphate,  5  ])ounds  sal  soda,  ;^  pints  annncjnia  (26°). 

*2  i>ounds  copper  sulphate,  15  pounds  sal  soda,  2  pints  annnonia  (26°). 
Ammoniacal  copper  carhonaie: 

*5  ounces  copper  carbonate,  H  pints  annnonia  (26°). 

*3  ounces  copper  carbonate,  2  pints  ammonia  (26°) . 

*  Prepared  and  tested  by  the  writer,  and  in  many  cases  also  testf^l  by  growers. 

The  preparation  of  the  copper  sprays  containing  different  chemical 
constituents  will  be  considered  in  the  order  in  which  they  appear  in 
the  preceding  list. 

COPPER   SULPilATE   SOLUTION. 

Copper  sulphate  (CuSO^.SHgO),  commonly  called  blue  vitriol  or 
bluestone,  forms,  when  dissolved  in  water,  one  of  the  most  active 
fiuigicides  known.  This  chemical,  the  composition,  manufacture,  and 
sources  of  supply  of  which  will  be  more  fully  considered  in  a  follow- 
ing chapter,  dissolves  in  cold  water,  but  somewhat  more  readily  in 
hot  water.  As  usually  sold,  the  crystals  are  large,  but  a  fine  form 
may  also  be  had  in  the  market.  If  the  large  crystals  are  purchased 
and  it  is  desired  to  dissolve  them  rapidly,  they  may  be  ground  in  a 
bone  or  shell  mill  before  placing  in  the  water.  This  has  frequently 
been  done  by  the  writer  when  quick  work  was  necessary. 

Copper  sulphate  may  be  manufactured  by  dissolving  the  black  oxide 
of  copper  in  sulphuric  acid,  or  by  the  various  modifications  of  this 
process  hereinafter  discussed.  A  watery  solution  of  this  chemical  is 
strongly  acid,  and  for  this  reason  a  simple  solution  of  copper  sulphate 
is  very  corrosive  and  injurious  tu  tender  plant  tissues,  as  foliage  and 
opening  ])uds.  To  avoid  this  injurious  action,  efforts  have  been  made 
to  obtain  from  the  copper  sulphate  solution  a  spray  retaining  the 
fungicidal  action  of  the  copper,  l)ut  by  the  addition  of  other  chemicals 
to  neutralize  or  largely  remove  its  acid  reaction  and  consequent  cor- 
rosive effects  upon  plants.  As  a  result  there  are  a  very  considerable 
number  of  copper  sprays,  representing  various  modifications  of  the 
simple  solution  of  copper  sulphate. 

Owing  to  the  acidity  of  a  solution  of  copper  sulphate,  the  sulphate 
should  not  be  dissolved  or  handled  in  metal  dishes  of  any  kind,  espe- 
cially those  of  iron.  The  copper  will  often  go  to  the  metal,  thus 
injuring  the  effectiveness  of  the  spray,  and  the  acid  may  also  injure 
or  destroy  the  dishes.     The  most  suitable  vessels  for  dissolving  copper 


148  PEACH    LEAF    CURL*.    ITS    NATURE    AND    TREATMENT. 

sulphate  for  work  xuch.  as  here  discussed  are  those  composed  wholly 
of  wood,  preferably  of  oak,  and  may  be  in  the  form  of  barrels,  casks, 
vats,  or  tanks,  of  a  capacity  corresponding*  to  the  respective  needs  of 
the  growers.  For  small  orchards  a  few  good  oak  barrels  of  45  or  60 
gallons  capacity  are  very  suitable.  As  concentrated  solutions  of  cop- 
per sulphate  can  be  made,  enough  of  the  sulphate  can  be  easily  dis- 
solved in  a  60-gallon  barrel  to  serve  for  300  or  even  1,200  gallons  of 
spray  when  properly  reduced.  It  is  well,  when  possible,  to  use  2 
gallons  of  water  to  each  pound  of  sulphate  when  dissolving  the  latter, 
but  stock  solutions  may  be  of  two  to  four  times  this  strength.  A 
solution  of  copper  sulphate  is  heavier  than  water,  so  that  it  is  an 
advantage  in  hastening  the  dissolving  process  to  retain  the  chemical 
near  the  top  of  the  water.  If  this  can  be  done,  the  heavier  copper 
solution  will  settle  to  the  bottom  of  the  Imrrel,  leaving  the  purer 
water  to  continue  the  dissolving  action  upon  the  sulphate.  The 
placing  of  the  copper  in  a  gunny  sack  and  suspending  the  latter  in 
the  water  has  been  recommended,  but  it  is  thought  that  other  means 
more  suitable  may  be  found.  The  use  of  sacks  or  other  cloths  about 
the  spraj^  tanks  is  hardly  advisable,  as  the  freer  the  tanks  are  kept 
from  lint,  strings,  fibers,  etc.,  arising  from  straining  cloths,  sacks, 
frayed  staves,  and  stirring  sticks,  the  less  trouble  the  sprayer  will 
have  with  his  nozzles  in  the  orchard,  and  the  better,  quicker,  and 
cheaper  can  the  spray  work  ])e  done. 

Instead  of  a  sack,  a  clean  willow  or  hard-wood  splint  basket  may  be 
used  for  suspending  the  chemicals.  A  box  may  also  be  easily  made 
for  the  purpose.  It  should  have  a  diameter,  when  about  1  foot 
deep,  sufficient  to  hold  the  copper  sulphate  to  be  dissolved,  and  it 
should  be  open  at  the  top,  with  strong  1-inch  slats  across  the  l)ottom, 
the  latter  to  be  set  one-fourth  inch  apart.  If  the  box  be  fitted  with 
a  strong  hoop  bail  it  may  be  suspended  in  the  barrel  by  placing  a  stick 
through  the  l)ail  and  across  the  top  of  the  barrel.  As  a  rule,  how- 
ever, the  writer  has  found  it  sufficient  to  place  the  copper  sulphate 
directly  in  the  bottom  of  a  good  oak  barrel,  filling  the  latter  one-third 
to  one-half  f idl  of  water,  and  stirring  and  crushing  the  crystals  with  a 
clean  hard-wood  pounder.  A  half  hour's  work  is  sufiicient  to  dissolve 
many  pounds  of  copper  sulphate  in  this  manner.  With  three  or  four 
good  barrels  one  man  can  thus  keep  a  large  spraying  gang  supplied 
with  material,  if  the  water  be  convenient.  It  is  always  an  advantage 
to  place  the  copper  in  water  in  the  barrels  over  night,  when  possible, 
as  sufficient  material  is  thus  easily  made  ready  in  the  morning  for  a 
half  day's  spraying.  It  is  an  advantage  to  strain  all  water  before  the 
copper  sulphate  is  added,  as  afterwards  ordinary  strainers  are  liable 
to  be  injured  by  the  acid,  and,  as  before  stated,  the  use  of  cloth 
strainers  is  not  advisable. 

The  eyes  and  hands  should  be  protected  as  nuich  as  possible  from 


PREPARATION  OF  THE  COPPER  SPRAYS.         149 

injiny  by  this  spra^v  (p.  171).  The  unaltered  solution  of  the  copper 
sulphate  is  not  only  unpleasant  to  handle  and  apply,  and  injurious  to 
tender  veo^etahle  tissues,  but  it  is  quite  injurious  to  all  metallic  parts 
of  pumps,  hose,  extension  rods,  and  nozzles,  nozzles  ])eing  eaten  out 
very  rapidl}'  by  it.  For  these  various  reasons  the  solution  of 
copper  sulphate  is  rarely  used  as  a  spray  in  an  munoditied  form.  In 
most  cases  its  corrosive  action  is  more  or  less  altered  or  lUHitralized 
through  the  addition  of  some  modif3nng  agent.  In  other  words,  the 
copper  sulphate  solution  is  used  as  a  base  or  stock  solution  for  the 
preparation  of  several  more  or  less  noninjurious  and  eipially  effective 
sprays,  as  the  Bordeaux  mixture,  the  eau  celeste,  the  modified  eau 
celeste,  the  ammoniacal  copper  carbonate,  etc.  For  this  purpose  it 
may  be  prepared  in  a  concentrated  solution,  to  be  used  as  a  stock 
solution  for  the  preparation  of  any  of  the  modified  sprays  mentioned, 
as  already  pointed  out. 

A  convenient  strength  for  stock  solutions  is  1  pound  of  copper  sul- 
phate to  1  or  2  gallons  of  water.  In  using  stock  solutions,  two  matters 
should  always  be  considered:  (1)  The  pails,  barrels,  or  tanks  used 
should  be  carefully  gauged  and  marked,  so  that  the  nvimber  of  gallons 
of  water  or  of  the  solution  they  contain  may  be  known  and  not  guessed 
at.^  (2)  Before  dipping  from  a  stock  solution  any  required  number 
of  gallons,  the  solution  should  be  thoroughly  stirred,  otherwise  the 
last  dipped  out  will  be  very  much  stronger  than  that  coming  from  the 
top,  and  consequently  the  work  will  be  inaccurate  and  often  very 
unsatisfactory;  moreover,  neglect  of  this  precaution  might,  in  many 
cases,  lead  to  the  injury  or  even  to  the  destruction  of  the  plants 
treated.  It  may  also  be  said  that  the  copper  sulphate  solution  should 
be  cold  when  used  in  the  preparation  of  Bordeaux  mixture,  eau  celeste, 
modified  eau  celeste,  or  ammoniacal  copper  car})onate. 

BORDEAUX    MIXTUKE. 

Bordeaux  mixture  is  prepared  b}'  uniting  the  milk  of  lime  with  a 
solution  of  copper  sulphate.  The  reaction  which  tak(\s  place  when 
the  two  solutions   are   united  as  well   as  the  other  chemical   phases 

'  The  following  rules  for  measuring  square  and  round  tanks  and  casks  may  prove 
of  value  in  this  connection: 

Circular  chleiiia. — ^lultiply  the  square  (jf  the  diameter  in  feet  by  tlio  deptli  in  feet 
and  the  product  by  5|  for  the  contents  in  gallons. 

Circular  ca.<<ks  or  harreh. — Multiply  the  square  of  the  average  diameter  in  inches  by 
34,' and  that  by  the  height  in  inches,  and  point  off  four  figures.  The  result  will  be 
the  contents  in  gallons  and  decimals  of  a  gallon.  The  average  diameter  of  a  barrel 
may  usually  be  obtained  by  adding  the  greatest  diameter  to  the  least  diameter  and 
dividing  by  2. 

Square  tanks. — ^Multiply  the  width  in  feet  by  the  length  in  feet,  and  that  by  the 
depth  in  feet,  and  that  again  by  TfV";?,  which  will  give  the  contents  i-n  gallons. 
Another  and  simple  nietliod  is  to  multiply  the  length,  width,  and  dei)th  in  inches, 
and  divide  by  231,  which  will  also  give  the  contents  in  gallons. 


150  PEACH    LEAF    CURL  I    ITS    NATURE    AISTD   TREATMENT. 

of  the  subject,  have  formed  the  base  for  much  discussion  and  investi- 
gation, which  it  is  not  necessary  to  consider  here,  especial!}^  as  these 
chemical  changes  are  various!}'  interpreted  by  different  writers. 
Those  interested  in  the  history  and  chemistry  of  Bordeaux  mixture 
may  learn  of  the  extensive  literature  upon  these  subjects  by  referring 
to  the  writings  of  Lodeman,^  Fairchild,^  and  others. 

In  the  union  of  the  milk  of  lime  with  a  solution  of  copper  sulphate 
there  is  produced  a  mixture  having  great  value  as  a  general  fungicide, 
and,  as  alreadj^  shown,  of  especial  value  for  the  treatment  of  peach 
leaf  curl.  The  mixture  possesses  several  advantages  for  orchard  work 
over  a  simple  solution  of  copper  sulphate:  (1)  The  addition  of  suffi- 
cient milk  of  lime  to  a  simple  solution  of  copper  sulphate  neutralizes 
the  acids  of  the  latter  to  such  an  extent  that  the  resulting  mixture  is 
practicall}^  noninjurious  to  foliage  and  buds,  while  still  retaining  the 
fungicidal  qualities  of  the  simple  sulphate  solution.  (2)  The  corrosive 
action  of  Bordeaux  mixture  upon  pumps,  pipes,  nozzles,  etc.,  is  com- 
paratively slight.  This  is  of  great  advantage  in  doing  uniform  and 
thorough  work.  (3)  The  lime  of  Bordeaux  mixture  causes  the  spray 
to  become  visible  upon  the  trees  sprayed,  and  while  this  is  not 
desirable  in  the  spraying  of  maturing  fruits,  and  is  avoided  by  adopt- 
ing other  sprays,  it  is  of  very  great  value  in  the  treatment  of  bare 
dormant  trees,  as  it  enables  the  workman  to  distinguish  the  sprayed 
from  the  unsprayed  portions  of  the  tree,  and  thus  to  complete  his 
work  more  thoroughly  than  could  otherwise  be  done.  In  case  of  the 
employment  of  hired  help  for  apph'ing  sprays,  as  is  usually  done,  the 
superintendent  or  owner  of  the  orchard  may  know  beyond  question 
by  the  appearance  of  the  trees  whether  or  not  his  men  are  doing  satis- 
factory work.  As  thoroughness  is  a  matter  of  prime  importance  in 
the  treatment  of  peach  leaf  curl,  too  much  stress  can  hardly  be  placed 
upon  this  advantage  of  Bordeaux  mixture  over  several  other  sprays. 
(4)  The  adhesive  qualities  of  Bordeaux  mixture  are  very  great, 
and  therefore  it  is  even  more  desirable  for  a  winter  than  for  a 
summer  spray.  This  is  especialh^  so  in  portions  of  the  country  where 
the  summers  are  dry,  as  on  the  Pacific  coast.  (5)  The  whitening  of 
the  trees  by  the  use  of  Bordeaux  mixture,  provided  the  spraying 
is  done  somewhat  early  in  the  winter,  is  claimed  to  retard  the  develop- 
ment of  the  buds.  The  unsprayed  trees  absorb  more  heat,  which 
causes  the  buds  to  swell  during  warm  days  in  winter,  thus  making 
them  liable  to  injury  from  subsequent  cold.^ 

The  methods  of  preparing  Bordeaux  mixture  for  large  and  small 
orchards  ma}^  vary  according  to  the  requirements  and  facilities  of  the 

^Lodeman,  E.  G.,  The  Spraying  of  Plants',  IMaemillan  &  Co.,  1896. 

^Fairchild,  D.  G.,  Bordeaux  Mixture  as  a  Fungicide,  Bull.  No.  6,  Division  of  Vege- 
table Pathology,  V.  S.  Dept.  of  Agr. 

'  Whitten,  J."  C,  Winter  Protection  of  the  Peach,  Mo.  Agr.  Exp.  Sta.  Bull.  No.  38. 
Some  of  the  conclusions  from  the  work  of  ]\Ir.  Whitten  are:  Whitening  the  twigs  and 
buds  by  spraying  thein  with  whitewa.sh  is  the  most  promising  method  of  winter  pro- 
tection tried  at  the  Missouri  Station;  whitened  buds  remained  practically  dormant 


PREPARATION  OF  THE  COPPER  SPRAYS.  151 

growers,  but  the  general  i)rinciples  involviHl  reinain  the  sanio.  As  a 
common  example,  the  manner  of  preparing  the  5-pound  formula  will 
bo  described:  In  a  -15  or  60  gallon  l)arrel  place  5  pounds  of  copper  sul- 
phate and  add  10  or  12  gallons  of  water.  Pound  and  stir  the  copper 
sulphate  until  wholly  dissolved.  In  a  half  barrel  slake  5  pounds  of 
quicklime  and  reduce  Avith  10  or  12  gallons  of  water.  Strain  the  milk 
of  lime  into  the  copper  solution,  stir  thoroughly,  and  add  sufficient 
water  to  make  45  gallons  in  all.  The  copper  and  lime  solutions  should 
both  be  cold  when  united.  When  the  water  is  added  and  the  whole  is 
well  stirred  the  spray  is  ready  to  be  applied. 

For  the  manner  of  preparing  the  stock  solution  of  copper  sulphate  to 
be  used  for  Bordeaux  mixture  the  reader  is  referred  to  pages  118  and 
liy,  where  full  instructions  will  be  found.  In  respect  to  the  addition  of 
lime  to  the  copper  solution,  it  may  be  said  that  the  milk  of  lime  result- 
ing from  the  slaking  of  2  pounds  of  good  quicklime  in  6  or  8  gallons 
of  water  is  sufficient  to  neutralize  a  solution  of  3  pounds  of  copper 
sulphate.  Larger  amounts  of  copper  should  receive  larger  amounts 
of  lime  in  proportion.  In  case  foliage  is  to  be  treated,  however,  it  is 
well  before  using  the  mixture  to  test  it  according  to  one  of  the  methods 
given, ^  or  to  bring  the  weight  of   quicklime  used  to  three-fourths, 

until  April,  when  unprotected  buds  swelled  perceptibly  during  warm  days  late  in 
Feliruary  and  early  in  March;  whitened  buds  blossomed  three  to  six  days  later  than 
unprotected  buds;  80  per  cent  of  whitened  buds  passed  the  winter  safely,  and  only 
20  per  cent  of  unwhitened  buds  passed  the  winter  unharmed.  These  facts  point  to 
those  sprays  having  lai-ge  amounts  of  lime  as  most  valuable  in  jirotecting  buds,  and 
they  should  be  considered  in  those  sections  of  the  c^buntry  where  the  buds  are  liable 
to  winter  injury.  A  fall  si)raying  may  also  be  a  decided  ailvantage  in  such  situations 
in  addition  to  the  early  Hi)ring  spraying  for  curl. 

See  also  on  this  subject  the  January  nimiber  of  the  Canadian  Horticulturist,  1899, 
pp.  1&-20. 

'  There  are  at  present  several  convenient  methods  practiced  in  making  Bordeaux 
mixture  to  determine  if  enough  lime  has  been  added  to  the  copper  sulphate  solution 
to  jjrevent  injury  when  the  mixture  is  applied  to  foliage.  We  adapt  the  following 
two  tests  from  Farmers'  Bulletin  No.  38  of  this  Department,  p.  7:  (o)  After  the 
milk  of  lime  and  cojjper  sulpliate  solutions  have  been  united  and  thoroughly  stirred, 
hold  the  blade  of  a  penknife  in  the  mixture  for  at  least  a  minute.  If  metallic  cojiper 
forms  on  the  blade  or  the  polished  steel  surface  assumes  the  color  of  copper  plate, 
the  mixture  is  still  corrosive  and  should  receive  more  milk  of  lime.  If  the  blade 
remains  unchanged,  the  mixture  may  be  safely  applied  to  most  foliage  under  favor- 
able weather  conditions,  {h)  Pour  some  of  the  mixture  into  a  saucer,  hold  between 
the  eyes  and  the  light,  and  breathe  gently  upon  it  for  at  least  half  a  minute.  If  the 
mixture  is  properly  made,  a  thin  pellicle,  looking  like  oil  on  water,  will  T^egin  to 
form  on  the  surface.  If  no  pellicle  forms,  more  milk  of  lime  should  be  added.  A  third 
test  (c)  maybe  made  with  a  20  per  cent  solution  of  ferrocyanide  of  potassium:  After 
the  milk  of  lime  is  added  to  the  copi)er  sulphate  solution,  and  the  whole  is  thoroughly 
stirred,  dip  uj)  a  coffee  cup  full  and  add  to  this  a  few  drops  of  the  ferrocyanide  of  potas- 
sium solution.  Allow  the  cup  to  stand  a  few  minutes  ami  then  pour  off  the  mixture 
carefully.  If  a  red  precipitate  is  found  at  the  l)ottom  of  the  cup,  the  mixture  requires 
more  milk  of  liuie,  which  should  he  a<lded  until  no  such  red  precipitate  is  formed 
when  the  test  is  repeated. 


152    PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

four-fifths,  or  five-sixths  of  the  weight  of  the  copper  sulphate  used. 
With  the  present  experiments  it  has  been  unnecessar}^  to  take  this 
matter  into  consideration,  for  the  spray  was  applied  to  dormant  trees, 
not  likely  to  be  injured  by  any  moderate  spray.  In  nearly  all  the  for- 
mulae tested  for  curl  the  pounds  of  lime  employed  were  equal  or 
greater  than  the  number  of  pounds  of  copper  sulphate  used. 

The  lime  used  in  preparing  Bordeaux  mixture  should  be  unslaked 
lime  or  quicklime  of  the  best  qualit3^  There  is  no  economy  in  using 
poor  lime,  and  air-slaked  lime  should  never  be  used.  The  use  of  poor 
or  air-slaked  lime  is  apt  to  result  in  an  imperfectly  neutralized,  and 
very  granular,  unsatisfactory  spray.  While  the  slaking  of  lime  and 
the  preparation  of  a  milk  of  lime  is  a  very  simple  matter,  it  is  one 
which  few  people  not  accustomed  to  the  process  will  do  well  the  first 
time.  If  not  properly  slaked,  there  are  apt  to  be  hard  particles  in  the 
spray,  causing  trouble  with  the  nozzles.  In  slaking  lime,  water  should 
be  added  to  the  lime  only  fast  enough  to  keep  it  from  overheating, 
adding  a  little  more  each  time  as  the  heat  increases.  With  some  lime 
the  use  of  a  little  hot  water  to  start  the  slaking  will  hasten  the  pro- 
cess. With  a  little  practice  this  work  can  be  done  so  as  to  result  in  a 
perfect  putty  or  cream  of  lime.  When  the  thick,  creamy  consistency 
is  obtained,  it  is  well  to  allow  the  mixture  to  stand  for  half  an  hour, 
if  possible,  while  hot,  being  sure  that  enough  water  is  present  to  pre- 
vent drying-  out.  If  the  Bordeaux  mixture  is  then  to  be  made,  cold 
water  should  be  added  to  the  lime  putty,  or  cream,  and  the  whole 
stirred  until  it  becomes  a  milk  of  lime  and  is  cool.  About  3  gallons 
of  water  should  l)e  added  for  each  pound  of  lime.  This  cool  or  cold 
milk  of  lime  should  now  ])e  strained  through  a  wire  sieve  or  strainer 
into  the  copper  sulphate  solution,  previously  prepared,  and  the  whole 
thoroughly  stirred. 

The  solution  of  copper  sulphate  should  also  be  cold  when  the  milk 
of  lime  is  added.  After  the  two  solutions  are  thoroughly  united  the 
mixture  may  be  reduced  to  the  required  amount  with  cold  water,  when 
the  spray  is  ready  for  use.  The  lime  and  copper  solutions  should 
never  be  united  more  than  a  few  hours  before  the  spray  is  to  be  applied. 
When  making  Bordeaux  mixture  wooden  vessels  should  be  used,  as 
barrels,  half  barrels,  tanks,  etc. 

For  peach  leaf  curl  the  amount  of  copper  sulphate  and  lime  to  be 
used  to  4:5  gallons  of  water  will  vary  according  to  the  views  of  the 
grower,  after  making  a  study  of  the  results  obtained  from  the  difi'erent 
formulae  tested  in  the  present  series  of  experiments. 


EAU   CELESTE. 


The  preparation  of  eau  celeste  is  verj^  simple.  To  each  2  pounds 
of  copper  sulphate  dissolved  in  6  or  8  gallons  of  water  add  3  pints  of 
strong  ammonia,  stir  thoroughl}',  and  dilute  to  45  gallons.     The  stock 


PREPARATION    OF    THE    COPPER    SPRAYS.  153 

solution  of  copper  sulphate  may  hi\  used  in  preparing  this  spray. 
Four  pounds  of  copper  to  3  pints  of  ammonia  for  45  gallons  of  water 
has  also  proved  an  effective  winter  spray. 

For  dormant  trees  this  spray  is  safe,  l)ut  for  the  treatment  of  foliage 
i t  is  too  corrosive  and  burning.  It  is  also  quite  corroding  to  nozzles  and 
other  metallic  portions  of  the  sprajang  outfit. 

MODIKIKI)    KAT    CKLESTK. 

The  modified  eau  celeste  is  less  injurious  to  foliage  than  the  eau 
celeste,  but  is  more  liable  to  injure  tender  leaves  and  buds  than  is  well- 
made  Bordeaux  mixture.  Its  preparation  is  nearly  as  simple  as  that 
of  the  eau  celeste.  To  -i  pounds  of  copper  sulphate  dissolved  in  10  or 
1'2  gallons  of  water  add  3  pints'  of  strong  ammonia,  dilute  with  water 
to  4:0  gallons,  and  stir  in  this  mixture  5  pounds  of  sal  soda  (common 
washing  soda)  until  dissolved.  In  preparing  this  spray  of  different 
strengths  the  same  proportions  of  the  chemicals  may  ))e  maintained. 


AMMONIACAL    COPPKR    CARBONATE. 


The  ammoniacal  copper  carbonate  spray  is  one  of  great  usefulness 
in  the  treatment  of  fruits  for  fungous  diseases,  especially  where  the 
spotting  of  fruits  b}"  the  ase  of  lime  is  to  be  avoided.  The  fungicidal 
value  of  this  spray  is,  however,  far  inferior  to  the  ordinary  Bordeaux 
mixture.  In  the  treatment  of  peach  leaf  curl  it  has  proved  less  satis- 
factory than  several  of  the  other  copper  spravs. 

The  manner  of  preparing  this  spraj'  is  simple.  Place  5  ounces  of 
copper  carbonate  in  the  bottom  of  a  3-gallon  crock.  From  a  2-gallon 
vessel  full  of  water  pour  about  one-half  pint  of  water  upon  the  copper 
carbonate  and  stir  the  latter  until  it  becomes  like  paste.  Mow  add  the 
remainder  of  the  2  gallons  of  water,  stir  again,  and  then  pour  into 
the  mixture  3  pints  of  2Cp  ammonia.  After  this  has  been  thoroughly 
stirred,  it  should  be  covered  and  allowed  to  stand  for  half  an  hour, 
when  the  whole  should  be  added  to  a  barrel  containing  43  gallons  of 
water.     When  well  mixed  this  spra}^  is  ready  to  l)e  applied. 

A  concentrated  solution  of  copper  carbonate  in  strong  ammonia  may 
be  made  as  above  described,  using  but  one-half  of  the  amount  of  water. 
If  su(;h  a  .solution  is  very  tighth'  stoppered  in  a  large  demijohn  or  jug 
it  may  be  kept  as  a  stock  solution,  ready  for  use  at  any  time.  By 
knowing  the  amount  of  copper  carbonate  in  each  quart  of  such  a  stock 
sohition  enough  may  be  measured  out  at  any  time  to  prepare  a  given 
number  of  gallons  of  spray  of  any  desired  strength. 

The  copper  carbonate  used  in  the  preparation  of  tlie  present  spray 
is  frequently  not  obtainal)le  in  quantity  at  the  drug  stores  in  smaller 
towns.  It  is  also  frecjucMitly  the  case  that  druggists  in  such  places 
charge  two  or  three  and  sometimes  four  or  fi\e  times  as  much  as  it  is 
worth,  making  the  ultimate  cost  of  the  spray  b(\vond  the  reach  of  the 


154  PEACH    LEAF    CURL*.    ITS    NATURE    AND    TREATMENT. 

grower.  For  this  reason  the  writer  gives,  on  page  183  of  this  bulletin, 
a  simple  way  of  preparing  the  copper  carbonate  on  the  farm  at  a 
minimum  figure.^ 

PREPARATION  OF  THE  SULPHUR  SPRATS. 

While  the  use  of  copper  sulphate  as  a  base  for  sprays  intended  for 
the  control  of  fungous  diseases  is  very  general,  there  are  special  dis- 
eases or  combinations  of  diseases  which  may  be  more  cheaply,  and 
often  more  successfully,  treated  with  sulphur  in  the  form  of  powder 
or  spray.  The  world-wide  use  of  sulphur  for  the  control  of  powder j^ 
mildew  of  the  grape  is  a  well-known  example.  It  is  also  known  that 
sulphur  possesses  valuable  insecticidal  qualities,  and  many  of  the  scale 
insects  and  mite  diseases  of  our  fruit  trees  may  be  readily  controlled 
by  the  use  of  sulphur  so  combined  and  prepared  as  to  be  applicable 
as  a  spray.  For  many  jenrs  the  most  successful  and  almost  the  only 
treatment  of  the  San  Jose  scale  on  the  Pacific  coast  has  been  by  sulphur 
sprays.  This  scale  is  very  injurious  to  peach  trees,  and  the  time  for 
the  application  of  sulphur  for  its  treatment  is  during  the  winter,  at  the 
time  of  treatment  for  peach  leaf  curl,  when  the  tree  is  dormant.  It 
has  already  been  shown  in  this  bulletin  that  such  a  winter  treatment 
of  the  peach  tree  with  sulphur  sprays  will  also  control  peach  leaf  curl. 
For  this  reason,  and  the  fact  that  the  San  Jose  scale  is  constantly 
spreading  throughout  the  East,  much  attention  is  here  given  to  the 
presentation  of  this  form  of  spray,  one  application  of  which  may  con- 
trol two  serious  diseases.  Experiments  conducted  by  the  writer  have 
shown  that  the  pear  leaf  mite  ma}^  be  controlled  by  the  winter  use  of 
sulphur  sprays,  and  it  is  thought  probable  that  their  use  will  also  con- 
trol the  oyster-shell  bark  louse  of  the  apple,  which  has  become  almost 
a  scourge  over  much  of  the  East  and  in  the  Pacific  Northwest. 

As  in  the  case  of  copper  sulphate  spraj^s,  it  has  also  been  found 
that  the  sulphur  sprays  may  be  most  satisfactorily  prepared  by  com- 

^  In  view  of  the  work  of  Mr.  C.  L.  Penny,  published  in  Bulletin  22  of  the  Delaware 
Agr.  Exp.  Sta. ,  1893,  the  amount  of  water  recommended  to  be  added  before  tlie  strong 
ammonia  water  is  poured  upon  the  carbonate  of  copper  is  nmch  greater  than  formerly 
used  by  the  Department.  IMr.  Penny  conducted  a  somewhat  extended  series  of 
exijeriments  to  ascertain  the  solubility  of  coj^per  carbonate  in  ammonia  gas  as  it  is 
contained  in  ammonia  water  of  different  strengths.  lie  found  that  a  given  amount 
of  ammonia  gas  in  a  weak  solution  of  ammonia  water  dissolves  more  copper  than  the 
same  amount  of  gas  in  a  strong  solution.  A  given  weight  of  ammonia  gas  in  a  2  to  4 
per  cent  solution  of  ammonia  water  dissolves  more  copper  carbonate  than  an  equal 
weight  of  gas  in  either  a  weaker  or  stronger  solution.  The  gas  in  a  2  to  4  per  cent 
ammonia  water  will  dissolve  its  own  weight  or  more  of  copper  carbonate.  On  the 
other  hand,  the  ammonia  gas  in  a  10  per  cent  solution  of  ammonia  water  will  dis- 
solve but  60  per  cent  of  its  weight  of  copper  carbonate,  and  ammonia  gas  in  a  20  per 
cent  solution  dissolves  only  about  35  per  cent  of  its  weight  of  copper.  Furthermore, 
the  ammonia  gas  contained  in  ammonia  water  of  less  than  2  per  cent  strength  rapidly 
loses  its  power  to  dissolve  copper  carbonate  as  the  solution  is  weakened. 


PREPARATION  OF  THE  SULPHUR  SPRAYS.         155 

billing  sulphur  with  lime.     Salt  has  also  been  used  in  connection  with 
these  springs  in  several  formulte. 

In  the  following  talile  are  shown  the  various  formultB  for  sulphur 
sprays  which  have  been  tested  for  the  control  of  peach  leaf  curl.  All 
fornuilse  are  for  45  gallons  of  water,  except  where  otherwise  stated. 

Table  42. — Sulphur  sprays  applied  for  the  control  of  peach  leaf  curl. 

*15  pounds  sulphur,  80  poun(is  lime,  10  pounds  salt,  (50  gallons  water. 
*10  pounds  sulphur,  20  i)oiuids  lime,  10  i)ounds  salt,  <)0  gallons  water. 
1 15  pounds  sulphur,  150  pounds  lime,  10  jxjunds  salt. 
*10  pounds  sulphur,  20  pounds  lime,  10  pounds  salt. 
1 10  pounds  sulphur,  20  pounds  lime,  5  pounds  salt. 
*5  pounds  sulphur,  10  pounds  lime,  5  pounds  salt. 

1 5  pounds  sulphur,  10  pounds  lime,  3  pounds  salt. 
1 15  pounds  sulphur,  30  pounds  lime. 

1 10  pounds  sulphur,  20  pomids  lime. 
1 10  pounds  sulphur,  8  pounds  lime. 

1 6  pounds  sulphur,  4  pounds  lime. 
1 5  pounds  sulphur,  15  pounds  lime. 
1 5  pomids  sulphur,  10  pounds  lime. 
1 5  pounds  sulphur,  5  pounds  lime. 

*  Recommended  by  the  ^Titter,  but  tested  by  the  growers. 

t  Prepared  and  tested  by  the  writer,  and  in  numerous  cases  also  tested  by  growers. 

It  takes  longer  and  is  more  difficult  to  prepare  the  sulphur  than  the 
copper  sprays;  but  where  the  sulphur  may  be  obtained  at  liberal  whole- 
sale rates  the  expense  of  the  two  classes  does  not  vary  greatly.  For 
facts  respecting  the  sources  of  sulphur,  etc. ,  the  reader  is  referred  to 
page  190. 

The  sulphur  sprays  are  prepared  by  boiling  the  ingredients  (sul- 
phur, lime,  and  salt,  or  sulphur  and  lime)  in  water  for  not  less  than 
two  hours.  So  far  as  the  writer's  experiments  are  concerned,  there 
has  resulted  no  apparent  advantage  in  the  treatment  of  curl  by  the 
addition  of  salt  to  these  sprays.  The  usual  method  which  growers 
having  small  orchards  folloAv  in  preparing  sulphur  sprays  is  to  slake 
one-third  to  one-half  of  the  lime  required,  in  the  vessel  in  which  the 
boiling  is  to  be  done.  When  slaked  to  a  thin  cream  the  sulphur  is 
stirred  in,  all  lumps  of  sulphur  having  been  first  pulverized.  Boiling 
water  is  now  added  to  make  one-half  to  two-thirds  the  amount  required 
l)y  the  formula.  This  mixture  is  boiled  for  not  less  than  one  and  one- 
half  hours,  only  boiling  water  being  added  if  it  becomes  necessary  to 
reduce  the  mixture.  If  the  boiling  is  done  in  a  kettle  or  iron  pan,  great 
care  is  necessary  to  prevent  the  caking  and  ])urning  of  the  materials. 
When  the  mixture  has  l)oiled  for  the  time  stated  or  longer,  the  remainder 
of  the  lime  is  slaked  and  the  salt  is  added  to  it  and  well  stirred  in.  This 
lime  and  salt  mixture  is  now  added  to  that  which  has  been  boiled  and  the 
boiling  is  continued  for  at  least  one-half  hour  longer.     The  boiled 


156    PEACH  LEAF  CUELI  ITS  NATURE  AND  TREATMENT. 

spray  should  now  be  strained  through  a  fine  wire  strainer  into  the 
spra}^  tank  or  barrel,  and  enough  boiling  water  added  to  make  up  the 
full  amount  of  spray  required  by  the  formula.  The  spray  maj^  be 
boiled  to  advantage  longer  than  two  hours,  but  should  never  be  boiled 
for  a  less  time  if  the  best  results  would  be  obtained.  The  sprays  should 
be  applied  to  the  trees  as  hot  as  possible.  The  spray  is  more  effective 
and  easier  to  apply  when  hot,  and  contact  with  the  air  cools  it  suffi- 
ciently so  that  twigs  of  dormant  trees  are  not  injured  by  the  heat. 

The  method  of  preparing  the  sulphur  sprays  here  outlined  is  prac- 
tically that  which  has  been  followed  in  California  for  many  j^ears. 
In  the  series  of  experiments  here  described,  however,  an  effort  has 
been  made  to  ascertain  if  salt  is  necessary  in  this  spraj^,  and  also 
whether  there  is  any  disadvantage  in  uniting  all  of  the  lime  and  sul- 
phur at  first.  After  a  comparison  of  the  results  obtained  from  sprays 
with  and  without  salt  and  of  those  in  which  the  lime  was  added  in  two 
portions  and  at  different  times  with  those  prepared  by  adding  all  of 
the  lime  and  sulphur  at  first,  it  has  not  been  possible  to  detect  any 
advantage  from  the  salt  nor  from  the  more  complex  method  of  pre- 
paring. This  relates,  of  course,  to  the  use  of  these  sprays  for  the  con- 
trol of  curl,  but  it  is  believed  that  the  same  will  hold  true  in  their  use 
for  the  control  of  insect  pests.  The  writer  has  personall}^  prepared 
and  tested  a  very  large  number  of  these  sprays,  and  recommends  the 
omission  of  salt,  and  further,  that  all  of  the  lime  and  sulphur  be  united 
and  reduced  with  boiling  water  before  the  cooking  begins  in  all  cases 
where  the  spray  is  to  be  applied  either  as  a  fungicide  or  insecticide, 
and  where  the  method  of  boiling  below  described  is  followed.  This 
will  both  cheapen  and  simplify  the  process. 

While  many  growers  may  feel  obliged  to  prepare  the  sulphur  sprays 
in  kettles  or  iron  pans,  experience  has  shown  that  they  may  be  boiled 
much  more  uniformly,  more  easily,  and  oftentimes  better  in  barrels  or 
wooden  tanks  by  using  live  steam  as  the  source  of  heat.  These  facts 
are  widely  recognized  on  the  Pacific  coast,  and  the  knowledge  is  put 
into  practice  by  some  of  the  leading  fruit  growers,  many  of  whom 
have  established  special  steam  cooking  plants  for  preparing  and  hand- 
ling the  sulphur  sprays.  Some  of  these  spray-cooking  appliances  are 
on  quite  an  extensive  scale  and  others  more  limited,  being  adapted  to 
the  needs  or  facilities  of  the  growers.  As  the  sulphur  spraj^s  have 
been  widely  used  in  California  and  Oregon,  and  are  likely  to  become 
much  more  generally  used  throughout  the  East,  especially  as  they  are 
particularly  intended  for  winter  application  to  all  deciduous  trees  and 
are  known  to  be  of  marked  value  both  as  insecticides  and  fungicides,  the 
more  improved  methods  of  preparing  them  will  be  of  general  interest 
to  orchardists,  and  several  are  here  given.  Three  types  of  cooking 
plants  are  described:  (1)  One  adapted  to  the  needs  of  an  orchard  of  10 
acres,  (2)  one  suited  to  the  needs  of  an  orchard  of  100  acres,  and  (3) 


PREPARATION    OF   THE    SULPHTTR    SPRAYS.  157 

one  of  sufficient  capacity  to  prepare  sprays  for  the  treatiiiciit  of  500  to 
1,000  acres  of  trees. 

For  small  orchards  sulphur  sprays  may  l)e  prepared  in  barrels  ])y 
the  use  of  steam.  Upon  a  solid  plank  platform  3  feet  wide,  12  feet 
lonof,  and  raised  18  inches  a])ove  the  ground,  place  three  oak  barrels 
hoUlino-  ()()  oaUons  each.  Each  barrel  should  have  a  ])unghole  through 
one  side  about  1  inch  above  the  bottom,  which  is  stopped'  with  a  long 
wooden  plug  while  the  spi-ay  is  boiling  in  the  barrel.  The  upper 
heads  of  the  barrels  should  be  removed,  and  each  maybe  nailed  in  two 
parts  to  serve  as  a  cover  for  the  barrel  whik^  the  spray  is  being  boiled. 
Near  one  end  of  the  row  of  ])arrels  is  set  the  boiler  in  which  steam  is 
to  ])e  generated.  From  the  dome  of  this  boiler  a  steam  pipe  should 
extend  horizontally  over  the  row  of  barrels,  and  not  less  than  2  feet 
above  them.  The  farther  end  extends  downward  at  a  right  angle,  by 
means  of  an  elbow,  to  within  6  inches  of  the  bottom  of  the  last  barrel. 
Where  the  pipe  passes  over  the  first  and  second  barrels,  downward- 
extending  pipes  are  connected  by  means  of  proper  couplings,  and 
extend  to  within  6  inches  of  the  bottoms  of  the  respective  barrels 
into  which  they  reach.  In  each  of  the  downward-extending  pipes  is 
fitted  a  valve  about  18  inches  above  the  barrels,  by  means  of  which  the 
inflow  of  steam  ma}'  be  controlled  for  each  barrel  separately.  The 
lower  end  of  each  of  the  pipes  leading  into  the  barrels  is  left  open 
for  the  escape  of  steam.  With  a  sufficient  head  of  steam  a  barrel  of 
water  may  l^e  brought  to  the  boiling  point  with  such  an  appliance  in 
about'five  minutes.  By  having  three  barrels,  as  here  suggested,  two 
may  be  kept  almost  constantly  filled  with  boiling  sprays,  while  the  third 
is  filled  with  boiling  water  for  use  in  slaking  lime,  filling  the  barrels 
after  the  sulphur  is  added,  and  reducing  the  spray  to  the  required 
amount  in  the  spray  tank.  With  such  an  appliance  for  boiling,  pro- 
vided the  two  barrels  for  spray  are  charged  alternately  one  hour  apart, 
60  gallons  of  well-made  spray  ma}^  be  sent  to  the  orchard  about  once  an 
hour,  after  allowing  each  lot  two  hours  of  constant  boiling.  In  pre- 
paring the  spray  for  l)oiling,  the  lime  is  first  slaked  to  a  cream  of  lime 
in  the  bottom  of  the  ])arrel,  the  pulverized  sulphur  is  stirred  in,  the 
l)arrel  is  filled  two-thirds  full  of  boiling  water,  a  top  is  placed  over 
the  barrel,  and  the  steam  is  turned  on  by  opening  the  valve  above  the 
barrel.  Within  a  very  few  minutes  the  steam  will  bring  the  contents 
to  a  seething  })oil.  and  this  can  be  maintained  for  the  two  hours 
required  without  danger  of  overheating  and  with  little  care,  except  of 
course  that  required  to  maintain  and  regulate  the  steam  supply.  The 
steam  stirs  the  spray  sufficientl)^  when  boiling.  When  thoroughly 
boiled  the  bunghole  near  the  bottom  of  the  barrel  is  opened  by  n^nov- 
ing  the  long  plug,  and  the  spray  is  drawn  off  into  pails  and  strained 
into  the  spray  tank  through  a  fine  wire  strainer.  When  the  barrel  is 
nearly  empty  enough  boiling  water  is  added  to  make  up  the  amount  of 


158    PEACH  LEAF  CUKLt  ITS  NATURE  AND  TREATMENT, 

spra}'  required  by  the  formula,  and  tliis  is  then  drawn  oti'.  Before  a 
new  charge  of  spray  materials  is  placed  in  the  l)arrel,  the  latter  should 
be  removed  from  beneath  the  steam  pipe  and  cleaned.  Convenient 
boilers  suited  to  boiling  one  or  more  barrels  of  spray  are  shown  in  the 
illustrations  given.     (PL  XXI.) 

For  orchards  of  100  acres  the  boiling  of  sprays  in  barrels  is  too 
slow.  The  plan  adopted  by  Mr.  A.  D.  Cutts,  at  the  Riviera  Orchard, 
will  here  be  given  as  admirably  answering  the  purpose  for  such 
orchards.  In  this  spray -boUing  plant  the  live  steam  is  olitained  from 
the  dome  of  the  boiler  of  a  20-horsepower  thrashing  engine,  and 
while  cooking  sprays  from  60  to  80  pounds  steam  pressure  is  main- 
tained. The  spray  is  boiled  in  two  rectangular  vats  or  tanks,  built  of 
2-inch  dressed  sugar  pine.  The  inside  measure  of  these  tanks  is, 
length  5  feet,  breadth  3  feet,  depth  30  inches.  These  tanks  have  the 
ends  mortised  into  the  side  and  bottom  planks  from  one-fourth  to 
three-eighths  of  an  inch.  Two  long  bolts  run  diagonally  across  at  each 
end  to  hold  the  head  in  place,  and  in  addition  the  planks  are  nailed 
together  with  lO**  cut  nails.  Each  of  these  tanks  will  hold  approxi 
mately  280  gallons  of  spray.  They  are  raised  -i  feet  above  the  ground 
upon  a  strong  and  well-braced  framework.  They  stand  side  by  side 
with  a  platform  between  about  4  feet  wide,  on  which  a  man  ma}^  stand 
to  attend  to  the  spray  while  boiling.  One  end  of  each  tank  is  toward 
the  boiler,  and  the  other,  which  is  supplied  with  a  faucet  or  sirup 
gate  for  drawing  off  the  spray,  extends  to  the  side  of  a  driveway. 
The  steam  is  supplied  to  each  of  the  tanks  directly  from  the  dome  of 
the  boiler.  From  the  steam  dome  a  l^-inch  pipe  leads  to  near  the 
ends  of  the  tanks.  This  is  connected  with  a  transverse  1  -inch  horizontal 
pipe  extending  laterally  to  a  point  opposite  the  center  of  each  tank  and 
level  with  the  tops  of  the  tanks.  The  ends  of  this  1-inch  pipe  now  turn 
at  a  right  angle  and  extend  to  the  center  of  the  top  of  the  ends  of  the 
tanks,  turn  down  on  the  inside  of  the  tanks  to  the  bottom  of  the  same, 
and  then  extend  along  the  center  of  the  bottom  to  near  the  farther  end, 
where  they  are  closed  by  having  an  iron  cap  screwed  over  the  end. 
Through  each  side  of  that  portion  of  the  1-inch  pipe  which  extends 
along  the  inside  of  the  bottom  of  each  tank  arc  drilled  6  small  holes 
for  the  escape  of  the  steam  into  the  tanks.  In  the  pipe  leading  to 
each  tank  is  placed  a  globe  valve  for  separately  controlling  or  prevent- 
ing the  flow  of  steam  to  each  of  the  tanks.  When  a  tank  of  spray  is 
ready  to  go  to  the  orchard,  the  spraj^  is  run  into  another  tank  situated 
on  a  low  truck  wagon,  the  truck  being  first  driven  under  the  end  of 
the  boiling  tank  which  is  to  be  emptied.  The  low  truck  with  the 
spray  is  then  driven  to  the  spray  tanks  in  the  orchard,  and  the  spray 
is  pumped  from  the  truck  tank  to  the  spray  tank,  without  delaying 
the  work  of  the  sprayers.  The  spray  is  strained  twice,  first  when  drawn 
off  from  the  boiling  vats  through  the  faucet,  and  second  when   it  is 


DESCRIPTION  OF  PLATE  XXI. 

Steam  spray-cooking  appliance.s  for  small  orchards.  Figs.  1  and  3  show  boilers  suited 
to  cooking  sprays  in  1  to  3  barrel  lots;  tig.  2  shows  a  boiler  connected  with  a  tank  in 
which  larger  quantities  of  spray  may  be  boiled  at  one  time.  These  cooking  appli- 
ances are  well  adapted  to  use  in  ten-acre  orchards  (p.  157) .  (Com]>ar-e  with  PI. 
XXII.) 


Bull.  20,  Div.  Veg.  Phys,  &  Path.,  U.  S,  Dept.  of  Agricultun 


Plate  XXI 


PKErABATlUN  OF  THK  SULPHUK  SPKAYS.         15U 

puinpod  from  the  truck  tank  into  the  spraj^  tank  in  the  orchard.  The 
brass  strainer  cloth  employed  by  tinners  in  making-  strainer  pails  is  used 
for  this  purpose.  It  is  very  necessary  to  strain  well,  as  in  the  unstrained 
spray  there  are  always  dregs  that  fill  the  nozzle  and  delay  work.  Mr. 
C\itts  says  that  in  tanks  of  this  kind  it  is  necessar}-  to  stir  the  spray 
frequently  while  boiling  to  thoroughly  mix  the  different  ingredients. 
Three  hours"  boiling  is  better  than  two.  He  also  says  that  one  man,  at 
$2  per  day,  will  tend  the  boiler  and  prepare  from  1,500  to  2,000  gallons 
of  spray  per  day,  and  that  it  will  require  about  one-half  cord  of 
4-foot  wood  to  generate  the  steam  in  such  a  boiler  as  he  uses. 

In  preparing  the  sulphur  sprays  for  orchards  containing  500  to 
1,000  acres  of  trees  it  is  desirable  to  have  tanks  of  larger  size  than 
those  used  by  Mr.  Cutts  and  to  avoid  as  much  pumping  and  trans- 
ferring of  the  sprays  as  possible.  One  of  the  most  convenient  and 
complete  spray -cooking  plants  for  orchards  of  large  size  which  has 
thus  far  been  seen  by  the  writer  will  here  be  described.  This  plant  is 
at  the  Rio  Bonito  orchard.  The  water  for  preparing  sprays  at  this 
orchard  is  obtained  from  a  well  and  is  forced  l)y  means  of  a  rotary 
force  pump  run  by  steam  power  into  a  large  storage  tank  elevated 
upon  a  heav}^  framework  some  30  feet  above  the  ground.  About 
10  feet  above  the  ground  and  at  one  corner  of  the  open  framework  of 
the  tank  house  is  placed  a  circular  tank  holding  about  300  gallons. 
This  is  a  storage  tank  to  receive  the  spray  when  prepared  for  the 
orchard.  The  bottom  of  this  circular  tank  is  supplied  with  steam 
pipes,  so  that  the  contents  may  be  kept  hot  and  ready  for  use.  From 
the  outer  side  of  this  storage  tank,  near  the  bottom,  is  a  discharge 
pipe  with  valve  and  hose  attached,  through  which  the  spra}'  may  be 
run  b}^  gravity  into  the  tops  of  the  300-gallon  spray  tanks  on  wagons 
which  are  used  in  the  orchard.  These  wagons  are  driven  to  the  side  of 
the  stoi-age  tank  and  filled  with  boiling  spray  in  a  few  minutes,  much 
as  street-sprinkling  tanks  are  driven  under  the  elevated  hydrants  and 
filled.  The  boiling  tank  proper  is  built  of  2-inch  surfaced  pine  plank 
within  a  firm  framework,  properly  bolted,  and  rests  firmly  upon  the 
ground.  It  is  situated  within  the  heavy  framework  of  the  water  tank 
house.  This  boiling  tank  is  approximately  18  feet  long,  3  feet  wide,  and 
3  feet  deep,  and  its  full  capacity  is  1,200  gallons.  In  the  center  of  the 
tank  house  is  a  water  pipe  connected  with  the  large  water  tank  above. 
Near  the  bottom  of  this  standpipe  are  hydrants  for  the  attachment  of 
hose,  thus  allowing  of  water  being  drawn  directly  from  the  water  supply 
above  into  the  boiling  tank  by  opening  a  h^'drant.  An  unlimited  supply 
of  cold  water  is  thus  alwa^^s  at  hand  without  the  necessity  of  lifting 
a  pailful  by  hand.  The  steam  pipe  for  heating  the  sprays  in  the  boil- 
ing tank  extends  from  end  to  end  along  the  bottom  within  the  wooden 
tank,  and  every  2  or  3  feet  along  this  pipe  are  cross  pipes  leading  toward 
each  side  of  the  tank.     The  ends  of  the  central  pipe  and  its  branches 


160    PEACH  LEAF  CUKL:  ITS  NATUEE  AND  TREATMENT. 

are  closed.  Along  both  sides  of  this  main  pipe  and  its  lateral 
branches  are  drilled  small  holes  for  the  escape  of  steam  into  the  tank. 
The  flow  of  steam  to  the  tank  is  controlled  by  means  of  a  globe  valve 
in  the  steam  supply  pipe,  the  valve  being-  conveniently  placed  for  the 
workman  at  the  tank.  Broad  board  covers  are  made  for  covering  the 
whole  tank  when  the  boiling  is  in  progress.  As  in  the  case  of  the 
spray-boiling  plant  of  Mr.  Cutts,  the  main  steam  pipe  leads  from  the 
tank  directly  to  the  steam  dome  of  the  boiler.  The  spray  is  prepared 
in  the  boiling  tank  of  double  strength,  and  when  sufficiently  boiled  is 
elevated  to  the  storage  tank  above  by  means  of  an  appliance  planned 
like  an  injector  of  a  boiler.  An  iron  pipe  about  2  inches  in  diameter 
leads  from  the  boiling  tank  upward  and  over  the  top  of  the  storage 
tank  described.  In  this  pipe  is  placed  the  injector,  which  is  supplied 
with  two  lateral  connections.  One  of  these  connections  is  with  the 
cold-water  supply  pipe,  and  the  other  is  with  the  main  steam  supply 
pipe.  In  each  of  the  pipes  connected  with  the  injector  are  placed 
globe  valves  for  the  control  of  the  inflow  of  water,  steam,  and  hot 
spray.  When  it  is  desired  to  fill  the  storage  tank  above  with  hot 
spray  from  the  boiling  tank  below,  the  valve  opening  into  the 
steam  pipe  leading  from  the  injector  to  the  steam  dome  is  opened. 
The  live  steam  at  once  escapes  through  the  injector  into  the  pipe 
leading  to  the  storage  tank  and  then  out  of  the  end  of  the  pipe. 
The  valves  leading  to  the  boiling  tank  and  the  cold-water  supply  are 
now  opened  in  such  a  manner  that  about  equal  parts  of  cold  water  and 
hot  spray  are  admitted  to  the  injector,  and  the  escaping  steam,  by 
means  of  its  tendency  to  form  a  vacuum,  soon  causes  a  combined 
stream  of  hot  spray  and  cold  water  to  follow  up  the  pipe  and  escape 
into  the  storage  tank  above.  There  is  thus  established  a  kind  of  steam 
siphon,  which  soon  carries  up  150  gallons  of  boiled  spray  and  an 
equal  amount  of  cold  water,  filling  the  300-gallon  storage  tank  with 
spray  of  the  required  strength,  the  strength  of  the  spray  in  the  boil- 
ing tank  being  double  that  required.  This  work  is  accomplished  by  a 
careful  adjustment  of  the  inflow  of  steam,  spray,  and  water  to  the 
injector,  the  storage  tank  being  filled  without  the  necessity  of  lifting 
a  pound  of  spray  b}^  hand.  The  combining  of  the  cold  water  with  the 
hot  spray  in  the  injector  is  found  to  be  necessary  to  the  proper  working 
of  the  latter  as  the  temperature  of  the  injector  would  otherwise  become 
too  high  for  efficient  work.  When  the  storage  tank  is  full,  steam  is 
turned  into  the  pipes  situated  at  its  bottom,  and  the  spray  is  again 
heated  to  the  boiling  point  and  kept  very  hot  until  drawn  off'  into  .a 
spray  tank  and  taken  to  the  orchard.  The  facilit}'  with  which  a  plant 
of  this  description  may  be  operated  will  depend  to  quite  an  extent  upon 
the  nature  and  capacity  of  the  boiler  used  for  generating  steam.  The 
more  easily  steam  can  be  generated  and  the  greater  capacity  for  steam 
which  the  boiler  possesses  the  better  for  the  work. 


3ull.  20,  Div.  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XXII. 


Steam  Spray-cooking  Appliances  for  Large  Orchards. 


DKSCKirTIOX  OF  PLATE  XXII. 

Fiir.  I  sliows  sulphur,  lime,  a nd  Halt  Hpray-t-ooking appliances  used  on  tiie  Kio  lionito 
Rancho.  Tlie  lieavv  franiewiiik  at  the  left  supports  a  larj^e  water  tauk  not  nhown 
in  the  photofrraph.  This  tank  is  tilled  ifroni  a  well  by  means  of  a  steam  rotary  forces 
l>unip,  and  sui»plies  all  water  required  in  cooking  and  reducing  sprays.  On  the 
irmund,  at  the  farther  side  of  the  framework  of  the  tank,  is  shown  a  long  wooden 
vat  from  which  steam  is  issuing.  This  rectangular  vat,  <le.scribed  on  page  159,  is  cajja- 
I)le  of  cooking  alx)ut  000  gallons  of  sulphur  sjjray  of  doul)le  strength,  and  is  seen  in 
full  operation  in  the  illustration,  the  heat  being  applied  by  means  of  steam  pi  pen  at 
the  bottom.  The  steam  pipe  is  shown  leading  from  the  dome  of  the  Ijoiler  in  the 
shed  at  the  right  and  in  the  backgromid  of  the  photograph.  The  round  tank  shown 
above  the  right  end  of  the  cooking  vat  holds  300  gallons  of  spray,  ready  for  appli- 
cation to  the  trees.  This  tank  is  tilled  from  the  cooking  vat  by  means  of  a  steam 
injector,  described  on  page  160,  and  the  spray  is  maintained  at  a  high  temperature 
by  means  of  steam  pipes  in  the  Ijottom,  as  in  case  of  the  cooking  vat  proper. 

Fig.  2  should  be  considered  in  connection  with  fig.  1.  The  large,  round  tank, 
standing  above  the  l)arrels,  is  the  storage  tank  for  sulphur  spray  after  it  has  been 
prepared  in  the  long  vat  below.  This  tank  holds  300  gallons — sufficient  spray  to  fill 
the  tank  seen  on  the  wagon.  The  wagon  tank  is  filled  l)y  gravity,  the  spray  flowing 
into  it  through  hose  running  direi-tly  from  a  spout  at  the  ))ottom  of  the  storage 
tank.  A  valve  in  this  spout  regulates  or  stops  this  flow  of  spray  as  desired.  One  of 
the  spray  wagons  used  in  this  large  orchard  is  shown.  The  pump  stands  crosswise 
l)ehind  the  corner  stakes  at  the  back  of  the  wagon.  These  stakes  serve  to  prevent 
the  hose  frftm  falling  beneath  the  wheels,  as  all  lines  of  ho.>:e  extend  from  the  rear  of 
the  wagou  when  in  use  in  the  orchard. 


PREPARATION  OF  COMBINED  COPPER  AND  SULPHUR  SPRAYS.  ICl 

By  referring  to  PI.  XXII  and  the  descriptions  of  tigures  the 
reader  may  obtain  a  good  idea  of  the  arrangement  of  this  extensive 
spray  cooking  plant,  as  well  as  of  the  boiler  supplying  steam. 

PREPARATION  OF  COMBINED  COPPER  AND  SULPHUR  SPRAYS  AND  NOTES  ON 
OTHER  SPRAYS  TESTED. 

For  many  years  the  use  of  combmed  copper  and  sulphur  sprays  has 
been  practiced  l)y  peach  growers  in  Oregon,  and  as  they  have  reported 
good  results  the  writer  prepared  the  following  four  formul{\3  of  this 
character  for  the  control  of  curl. 

BORDEAUX    MIXTURE    AND    SULPHUR   SPRAYS   COMBINED. 

The  formulre  of  the  combined  Bordeaux  mixture  and  sulphur 
sprays  tested  are  given  in  the  following  list: 

List  of  sulphur  sprays  coinhined  wiUi  Bordeaux  mixture. 

3  pounds  copper  sulphate,  10  pounds  sulphur,  20  pounds  lime. 
3  pounds  copper  sulphate,  10  pounds  sulphur,  10  pounds  lime. 
3  pounds  copper  sulphate,  5  pounds  sulphur,  10  pounds  lime. 
2  povmds  copper  sulphate,    5  pounds  sulphur,  10  pounds  lime. 

In  preparing  these  combined  sprays,  which  were  found  somewhat 
more  effective  in  the  control  of  peach  leaf  curl  than  the  sulphur  sprays 
alone,  the  Bordeaux  mixture  was  added  to  the  fully  prepared  sulphur 
spray.  A  portion  of  the  lime  given  in  the  formula  was  reserved  for 
making  the  Bordeaux  mixture,  while  the  remainder  of  the  lime  was 
comljined  and  boiled  with  the  sulphur  in  the  manner  already  described. 
When  the  sulphur  spraj'  had  been  placed  in  the  spray  tank,  the  Bor- 
deaux mixture,  which  had  been  freshly  prepared  from  the  copper 
sulphate  and  the  remainder  of  the  lime,  was  added,  and  after  thorough 
mixing  was  at  once  applied  to  the  trees.  The  union  of  the  yellow 
sulphur  spray  with  the  blue  Bordeaux  mixture  forms  a  spray  of  a 
distinct  green  color.  The  application  of  this  spray  is  similar  to  that 
of  the  sulphur  spra}^,  requiring  the  same  class  of  nozzles. 

MISCELLANEOUS   SPRAYS. 

A  large  number  of  sprat's  not  included  in  the  preceding  descrip- 
tions have  been  prepared  and  tested  for  peach  leaf  curl,  and  some  of 
them  have  been  discussed  in  other  portions  of  this  bulletin.  Several 
of  them  were  tested  for  the  purpose  of  learning  the  value  of  the 
separate  ingredients  of  the  leading  sprays,  as  salt,  lime,  etc.  Among 
these  were  lime,  applied  as  a  simple  milk  of  lime;  salt,  applied  in 
solutions  of  different  strengths;  and  lime  and  .salt  combined,  applied  as 
a  whitewash.  Sulphur  was  tested  in  the  form  of  sulphide  of  potassium, 
applied  in  various  strengths  in  liquid  form,  and  the  union  of  this  sul- 
phide of  potassium  with  milk  of  lime  was  also  tested.  Iron  sidphate, 
19093— No.  20 11 


•162  PEACH    LEAF    CURL:    ITS    NATURE    AND    TREATMENT. 

sulphur,  and  lime  were  tested  iu  combination  by  adding  to  the  sulphur 
spraj'  a  mixture  prepared  b}^  uniting  the  milk  of  lime  with  a  solution 
of  iron  sulphate.  The  union  of  the  milk  of  lime  with  the  iron  sulphate 
solution  produced  a  lead-colored  mixture  resembling  Bordeaux  mix- 
ture in  consistency,  and  when  united  with  the  sulphur  solution  the 
color  was  dark  green  or  approaching  black.  Iron  sulphate  and  lime 
were  also  tested  separately. 

While  some  of  these  sprays  gaye  eyidence  of  considerable  fungi- 
cidal action,  none  of  them  gaye  results  which  Ayould  warrant  their 
substitution  for  the  sprays  already  considered  in  preyious  chapters, 
and  hence  it  is  unnecessary  to  enter  further  into  details  respecting 
their  preparation.  The  results  of  their  use  may  be  learned  in  the 
chapters  of  this  bulletin  which  relate  to  the  action  of  the  sprays  on 
the  foliage  and  the  fruit. 

GENERAL    CHARACTERS    OF   THE    SPRAYS   TESTED. 

There  are  certain  general  characters  of  sprays  adapting  them  or 
making  them  unsuitable  for  yarious  classes  of  work,  and  to  these  it 
may  be  well  to  allude. 

THE    EXin'RIXG    QrALITIES   OF   THE   SPRAYS. 

In  the  worK  here  described  careful  notes  were  made  on  the  enduring 
or  weathering  qualities  of  the  sprays  tested. 

During  the  last  week  in  April  and  first  week  in  March,  1895,  35 
sprays,  of  different  formulte,  were  applied  in  the  experimental  block 
in  the  Eio  Bonito  orchard,  most  of  them  to  10  large  trees,  as  has 
heretofore  been  shown.  On  August  10,  or  fiye  months  after  the 
spraying  was  completed,  the  trees  of  each  experiment  row  were 
examined  to'  ascertain  as  far  as  possible  the  enduring  or  weathering 
qualities  of  the  sprays,  and  according  to  the  notes  made  at  that  time 
the  appearance  of  the  sprays  upon  the  trees,  after  fiye  months'  weather- 
ing, maj'  be  grouped  under  the  following  four  heads  or  classes; 

(1)  Sprays  showing  quite  distinctly  upon  the  trees  on  August  10. 

(2)  Sprays  moderately  eyident  on  August  10. 

(3)  Sprays  little  eyident  on  August  10. 
(1)  Sprays  not  obseryable  on  August  10. 

The  spra3"s  classed  under  the  first  head,  were  those  applied  to  rows  1, 
3,  7,  9,  13,  15,  18,  19,  21,  22,  25,  33,  36,  11,  11,  15,  50.  51,  56,  and  57; 
under  the  second  head,  those  applied  to  rows  6,  10,  12,  16,  28,  12,  48, 
and  51;  under  the  third  head,  those  applied  to  rows  27  and  35;  and 
under  the  fourth  head,  those  applied  to  rows  30,  32,  38,  39,  and  47. 
By  referring  to  page  73  the  reader  will  find  a  table  giying  the  formulae 
for  sprays  applied  to  each  of  the  rows  named,  and  an  examination  of 
these  formulae  will  bring  out  the  following  facts:    All  the  sprays 


GENERAL    CHARACTERS    OF   THE   SPRAYS   TESTED.  163 

included  under  the  first  two  headings  contain  lime,  while  those  under 
headings  3  and  4  contain  none;  all  formula'  containing  15,  20,  or  30 
pounds  of  lime  to  45  gallons  of  water  fall  under  tiie  lirst  head.  Of  the 
18  sprat's  containing  4,  6,  8,  and  10  pounds  of  lime,  10  fall  under  the 
first  heading  and  8  under  the  second:  copper  sulphate  enters  into  the 
composition  of  8  of  the  10  sprays  falling  under  the  first  head,  while 
the  remaining  2  contain  iron  sulphate;  of  the  8  sprays  which  fall  under 
the  second  heading,  only  1  contains  copper  sulphate,  and  that  but  2 
pounds,  while  5  are  sulphur  sprays. 

These  facts  seem  to  show  that  the  union  of  copper  sulphate  and  lime 
produces  a  spray  possessing  decidedly  greater  weathering  qualities 
than  the  union  of  sulphur  and  lime. 

In  the  following  list  are  shown  the  pounds  of  lime  contained  in  the 
various  sprays  tested;  the  numbers  of  the  rows  of  trees  to  which  each 
amount  of  lime  was  applied;  the  position  of  each  spray  as  grouped 
according  to  its  apparent  weathering  qualities  into  classes  1,  2.  3,  or 
4;  and  references  showing  the  nature  of  all  the  sprays  containing  lime: 

Weather-resist h7g  rjualities  of  sprays. 

30  pounds  lime  in  formula,  class  1,  rows  1 1  and  7t. 

20  pounds  lime  in  formula,  class  1,  rows  3t,  9t,  13t,  36t*,  and  44°. 

15  pound.s  lime  in  formula,  class  1,  rows  15*,  33*,  and  57t. 

10  pounds   lime  in  formula,  class  1,  rows  18t*,  19t*,  41*  45*,  50tt,  54*,  and  56ttt; 

class  2,  rows  Gf,  12t,  and  48t°. 
8  pounds  lime  in  formula,  class  2,  row  lOf. 
5  pounds  lime  in  formula,  class  1,  rows    21*,  22*,  25*;  class  2,  rows  28*,  42t°,  and 

51t. 
4  pounds  lime  in  formula,  class  2,  row  16t. 
No  lime  in  formula,  cla-s  3,  rows  27  and  35;  class  4,  rows  30,  32,  38,  39  and  47. 


t  Sulphur  and  lime,  or  sulphur,  lime,  and  salt. 

t*  Copper  sulphate,  sulphur,  and  lime. 

°Lime. 

*  Copper  sulphate  and  lime. 

tt  Iron  sulphate  and  lime. 

ttt  Iron  sulphate,  sulphur,  and  lime. 

t°  Potassium  sulphide  and  lime. 

It  may  be  well  to  state  in  connection  with  the  above  list  that  while 
all  the  .sprays  not  containing  lime  are  clas.sed  under  the  third  and 
fourth  heads,  this  arrangement  ma}'  not  correctly  represent  their 
respective  enduring  qualities.  As  they  are  without  lime,  the  eye  can 
not  detect  their  presence  in  manj-  cases  where  it  is  possible  the  chemi- 
cals may  realh'  be  present  in  effective  quantity,  and  it  is  therefore 
apparent  that  the  value  of  such  a  list  is  largely  of  a  comparative 
nature  among  those  spra3's  containing  more  or  less  lime  in  various 
combinations. 

The  general  facts  appear  to  be.  as  already  indicated,  that  the  copper 
sprays  are  more  enduring  than  the  sulphur  sprays,  considering  pound 


164    PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

for  pound  of  lime  iu  their  composition,  and  also  that  the  amount  of 
lime  may  be  much  less  in  the  copper  than  in  the  sulphur  sprays  and 
still  maintain  the  enduring  qualities.  It  is  likewise  the  opinion  of  the 
writer  that  where  a  winter  spray  of  copper  and  lime  has  proved  of 
poorer  weathering  quality  than  is  desirable  in  a  given  climate,  the  cop- 
per should  be  increased  as  well  as  the  lime  when  greater  resistance  to 
weathering  is  sought.  In  other  words,  while  the  increase  of  lime 
enhances  the  weathering  qualities  of  the  spray,  it  also  has  a  tendency 
to  retard  or  obscure  the  action  of  the  copper  it  contains,  unless  the 
latter  is  increased  somewhat  in  proportion  to  the  increase  of  lime. 

THE   CORROSIVE    ACTION    OF   THE   SPRAYS. 

As  the  present  use  of  sprays  has  been  limited  to  their  winter  appli- 
cation, the  notes  on  their  corrosive  action  relate  largely  to  the  action 
upon  dormant  trees  or  upon  the  vegetation  immediately  following 
the  commencement  of  spring  growth.  In  each  case  these  remarks 
relate  to  the  use  of  sprays  upon  peach  trees,  which  are  known  to  be 
among  the  most  tender  deciduous  fruit  trees  commonly  grown  in  the 
temperate  zone. 

The  sulphur  sprays  of  the  greater  strengths  used  in  these  experi- 
ments caused  in  many  cases  the  loss  of  some  of  the  liner  and  weaker  inner 
growth  of  the  trees.  This  is  more  apt  to  be  the  case,  it  is  believed, 
when  the  spraj"  is  applied  shortly  before  growth  begins  in  the  spring. 
Where  very  strong  sprays  of  this  class  are  to  be  used,  it  is  well  to 
apply  them  comparatively  early  in  the  dormant  period,  say  four  weeks 
earlier  than  the  copper  sprays.  Sprays  having  not  more  than  10  pounds 
of  sulphur  to  15  gallons  of  spray  may  be  used  with  little  danger  up 
to  within  four  weeks  of  the  swelling  of  the  buds. 

There  is  no  danger  of  injuring  twigs  or  buds  with  the  copper  sprays  if 
properly  prepared  and  applied  before  the  buds  have  opened.  Well- 
made  Bordeaux  mixture  may  be  used  even  as  late  as  the  opening  of  the 
first  blossom  buds.  The  ammoniacal  copper  carbonate  may  also  be  safely 
used  to  a  late  date,  and  both  may  be  again  applied,  if  desired,  after  the 
trees  have  passed  out  of  bloom.  The  simple  solution  of  copper  sul- 
phate and  the  eau  celeste  may  be  safely  used  to  within  a  week  of  the 
opening  of  peach  buds,  but  they  should  never  be  used  upon  the  foliage 
of  the  tree.  Modified  eau  celeste  is  less  corrosive  than  the  eau  celeste, 
and  may  be  used  until  the  first  buds  begin  to  open,  but  from  observa- 
tion in  other  classes  of  spray  work  it  is  believed  to  be  unsafe  to  apply 
this  spray  to  the  leaves  of  the  peach. 

The  injurious  action  of  the  sulphur  sprays  when  combined  with  Bor- 
deaux mixture  is  fairh^  to  be  compared  with  the  action  of  the  sulphur 
spraj^s  alone  when  containing  equal  amounts  of  sulphur. 

The  spray  composed  of  iron  sulphate  and  lime  is  more  apt  to  injure 
tender  shoots  and  buds  than  the  Bordeaux  mixture,  and  such  a  spray 
can  not  be  recommended  for  use  upon  foliage. 


GENERAL    CHARACTERS    OF    THE    SPRAYS   TESTED.  165 

Milk  of  lime  appears  to  he  practically  harmless  when  applied  to 
dormant  trees  or  to  trees  in  leaf;  hence  any  injurious  action  resulting 
from  the  use  of  sprays  containing  lime  should  he  charged  to  the  other 
ingredients  or  to  the  lime  as  altered  or  moditied  through  combination 
with  such  other  constituents. 

ADVANTAGES    OF    DISCERNIBLE    AND    INDISCERNIBLE   SPRAYS. 

Reference  has  been  made  in  a  brief  way  to  the  advantages  possessed 
bj^  certain  sprays  in  forming  a  visible  deposit  upon  the  surfaces 
sprayed.  While  sprays  forming  such  a  visible  deposit  are  decidedly 
advantageous  for  all  winter  work,  those  leaving  no  such  disthict  deposit 
are  most  desirable  for  the  treatment  of  fruit,  especially  when  approach- 
ing maturity.  The  advantages  of  white  sprays  in  the  winter  treat- 
ment of  deciduous  trees  are  obvious,  it  being  possible  with  such  sprays 
to  clearly  see  what  portions  of  the  plant  have  been  thoroughly  and 
properl}'^  covered.  This  advantage  may  even  make  the  difference 
between  success  and  failure  in  the  work. 

Some  recent  experiments  in  apph^ng  whitewash  or  sprays  contain- 
ing large  amounts  of  lime  have  tended  to  show  that  the  opening  of  the 
buds  may  be  somewhat  retarded  by  such  winter  treatment.  The  theory 
is  that  whitening  the  trees  prevents,  to  some  extent,  their  absorption 
of  heat  from  the  sun's  rays,  and  that  this  aids  in  keeping  the  trees  in 
a  dormant  condition  somewhat  later  than  would  otherwise  be  the  case. 
Whether  this  will  prove  of  enough  importance  to  warrant  the  outla}' 
for  spraying  remains  to  he  shown.  An  illustrated  article  on  this  sub- 
ject appeared  in  the  Canadian  Horticulturist  for  January.  1899.^ 

All  sprays,  both  copper  and  sulphur,  which  contain  lime  are  adapted 
to  the  purposes  here  considered.  The  Bordeaux  mixtures  and  sulphur 
sprays  used  in  the  work  descril)ed  are  distinctly  observable  upon  the 
trees  when  applied,  and  after  drying  for  a  very  short  time  the  treated 
trees  become  decided!}'  white.  The  greater  the  amount  of  lime  the 
whiter  the  trees.     (Pl.^  XXIII.) 

In  the  summer  treatment  of  trees  and  plants  having  fruit  approach- 
ing maturity,  the  use  of  clear  sprat's  is  often  most  to  be  recommended. 
The  spray  now  best  adapted  for  this  purpose  is  the  ammoniacal 
copper  carbonate.  A  stronger  spray,  though  making  less  showing 
than  Bordeaux  mixture,  is  the  modified  eau  celeste.  As  this  is  apt 
to  cause  injury  in  some  cases,  it  is  desirable  to  use  Bordeaux  mixture 
for  summer  work  up  to  a  date  when  the  fruit  is  approaching  maturity, 
and  then  to  adopt  the  ammoniacal  copper  carbonate.  The  time  at 
which  the  summer  use  of  Bordeaux  mixture  should  be  discarded  for  the 
ammoniacal  copper  carljonate  will  depend  largely  upon  the  amount 
of  summer  rains  in  the  locality'  where  used.  In  New  York  State,  for 
instance,  where  summer  showers  are  frequent,  the   lime-containing 

*  Orr,  W.  M.,  1.  c,  pp.  18-20.     See  further  remarks  on  this  subject  on  p.  150. 


166         PEACH    LEAF    CURL*.    ITS    NATURE    AND    TREATMENT. 

Bordeaux  mixture  could  be  used  upon  fruit  until  a  later  date  in  the 
summer  than  it  could  in  California,  where  almost  no  summer  showers 
occur,  and  where  the  lime  would  remain  upon  the  fruit  until  the  latter 
was  mature.  This  matter  leads  us  naturally  to  the  consideration  of 
sprat's  adapted  for  wet  and  for  dry  localities. 

SPRAYS   ADAPTED   TO    USE   IN    WET    AND    IN    DRY    LOCALITIES. 

Little  can  be  said  on  this  subject  that  has  not  been  previously 
touched  upon  in  this  bulletin.  A  few  general  remarks,  however, 
ma}^  be  of  advantage  to  the  grower.  The  enduring  qualities  of  sprat's 
containing  lime  increase  w^here  the  ratio  of  the  other  ingredients  is 
maintained,  very  largely  in  proportion  to  the  increase  of  the  lime 
which  the  formula?  contain.  For  instance,  the  relative  proportions  of 
copper  sulphate  and  lime  being  maintained,  a  Bordeaux  mixture 
which  contains  10  pounds  of  lime  to  15  gallons  of  spray  will  obviously 
endure  much  longer  upon  the  trees  in  a  wet  climate  than  a  Bordeaux 
mixture  containing  but  5  pounds  of  lime  to  the  same  amount  of  spray. 
To  avoid  the  loss  in  activity  and  effectiveness  of  a  spray  containing  a 
large  amount  of  lime,  the  fungicide,  be  it  copper  or  sulphur,  should 
be  increased  so  as  to  maintain  the  same  or  nearly  the  same  ratio 
between  the  copper  and  lime  which  exists  in  the  spray  containing  less 
lime.  It  is  advised,  therefore,  that  sprays  to  be  used  in  a  wet  climate, 
especialh^  those  intended  for  winter  application,  should  be  made 
stronger,  both  in  lime  and  in  the  essential  fungicide  they  contain, 
than  is  found  necessary  in  a  dry  climate.  If  two  spraj-ings  are  neces- 
sary, both  should  be  given  the  dormant  trees. 

In  wet  climates  the  conditions  favorable  to  the  development  of  curl 
and  other  fungous  diseases  are  increased.  This  supplies  a  further 
reason  for  using  sprays  containing  increased  amounts  of  fungicide  and 
having  greater  enduring  qualities  than  sprays  used  in  dr^'  localities. 
The  soil  conditions  in  wet  situations  are  apt  to  delay  spray  work  till  the 
last  moment  compatible  with  effective  work.  In  such  cases  the  amount 
of  copper  should  be  sufficient,  if  this  class  of  sprays  be  used,  to  act 
promptly.  If  the  Bordeaux  mixture  be  applied  under  such  circum- 
stances, it  will  not  be  found  desirable  to  reduce  the  copper  below-  the 
equivalent  of  1  pound  of  copper  for  each  pound  of  lime,  and  a  higher 
proportion  may  often  be  used  to  advautange  on  dormant  trees. 


CHAPTER  IX. 

THE  APPLICATION  OF  SPRAYS. 
GENERAL   ACCESSORIES   FOK    WINTER    SPRAYING. 

To  tliose  who  have  sprayed  for  3'ears  and  have  learned  T)v  experience 
the  most  suitable  appliances  for  such  work  the  present  remarks  may 
not  prove  of  direct  value.  They  are  especially  intended,  however,  for 
those  undertaking"  such  work  for  the  first  time. 

NOZZLES    SUITED    TO    WINTER    WORK. 

The  past  few  years  have  seen  in  the  United  States  a  very  great 
increas-e  in  the  styles  and  places  of  manufacture  of  nozzles  and  other 
spraying  appliances.  At  the  present  time  the  number  of  stjdes  and 
makes  of  nozzles  often  leads  to  confusion  in  the  mind  of  the  prospective 
sprayer.  In  fact,  however,  there  are  but  few  essential  features  to  a  good 
nozzle.  The  form  of  greatest  importance  for  most  classes  of  work  is 
that  which  gives  to  the  discharged  spray  a  rotary  or  cvclone  motion. 
This  movement  is  given  in  a  very  simple  manner  by  admitting  the 
stream  at  an  angle  into  a  circular  chamber  in  the  nozzle,  so  that  it  first 
strikes  the  curving  side  of  the  chamber,  and  is  thus  forced  to  assume 
a  circular  or  rotary  motion.  The  revolving  stream  then  passes  through 
the  small  central  opening  of  the  discharge  plate  and  widens  into  a  cone- 
shaped  spray,  which  gives  to  this  nozzle  certain  advantages  not  enjoyed 
by  several  other  types  now  on  the  market.  Spray  from  such  a  nozzle 
covers  a  greater  area  without  moving  the  nozzle  than  is  covered  with 
most  other  types.  There  are  nozzles,  however,  capable  of  throwing 
spray  to  greater  heights.  The  rotary  motion  assumed  by  the  spra}'  in 
the  cyclone  or  Yermorel  nozzles  is  a  dissipation  of  force,  at  least  in 
most  forms  of  these  nozzles,  so  far  as  concerns  the  throwing  of  sprays 
to  a  great  distance.  A  type  of  nozzle  first  used  near  San  Jose.  Cal., 
and  now  bearing  the  name. of  that  town,  is  perhaps  better  adapted  to 
long-distance  spraying,  and  has  been  extensively  used  on  the  Pacific 
coast.  The  spray  is  formed  by  the  tiuid  passing,  under  high  pressure, 
through  a  narrow  slit  in  a  rubber  or  metallic  plate.  Where  the  rubber 
plate  is  used  the  escape  of  small  particles  may  take  place  through  the 
temporary  expansion  of  the  opening  in  the  plate. 

The  cyclone  nozzles  are  now  made  by  many  manufacturers  in  difi'erent 
portions  of  the  country,  and  may  be  obtained  through  any  first-class 

167 


168 


PEACH  LEAF  CURLI  ITS  NATURE  AND  TREATMENT. 


Fig.  1.— Cyclone  nozzle, 
with  direct  discharge 
and  degorger,  for  thin 
sprays. 


hardware  dealer  in  the  United  States.     The  San  Jose  nozzle  is  also 
obtainable  through  hardware  dealers  generally. 

There  are  many  types  and  styles  of  cyclone  nozzles.  Some  are  planned 
to  throw  the  spray  away  from  the  workman,  with  direct  or  forward 
discharge  (fig.  1).  Others  are  so  constructed  that  the 
spray  is  discharged  laterally  or  at  a  more  or  less 
acute  angle  (figs.  2  and  3).  In  using  these  nozzles 
for  winter  work  on  deciduous  trees  it  has  been  found 
that  most  thorough  and  most  satisfactory  work  can 
be  done  with  less  waste  of  spray  when  nozzles  having 
a  lateral  discharge  are  emploj^ed.  The  reasons  for 
this  are  evident.  Dormant  deciduous  trees  are  but 
a  skeleton  or  framework,  presenting  to  the  sprayer 
but  a  limited  surface  for  stopping  a  direct  spray. 
For  this  reason,  where  a  nozzle  hav- 
ing a  direct  discharge  is  emplo^xd,  a 
large  portion  of  the  spra}'  will  of 
necessity'  pass  through  the  limbs  of  the  tree  and  fall  upon 
the  ground,  while  at  best  it  will  pass  through  the  tree  but 
once.  By  using  the  cyclone  nozzle  with  lateral  discharge, 
however,  the  cone  of  spray  may  be  directed  upward 
through  the  whole  top,  and  in  falling  back  it  passes  through 
the  tree  a  second  time.  Here  is  a  decided  gain  in  the 
limb  surface  which  will  be  reached  by  the  use  of  a  given 
amount  of  spray.  The  nozzle  having  lateral  discharge 
can  also  be  handled  to  much  greater  advantage  than  the 
nozzle  with  direct  discharge.  By  turning  the  extension 
pipe  which  bears  the  nozzle,  the  cone  of  spray  may  lie 

directed  upward,  downward,  or  laterally  upon 
the  limbs  as  desired.  This  has  proven  of  great 
advantage  in  doing  thorough  work. 

The  ordinary  lateral  discharge  cyclone  nozzles 
are  suitable  for  use  with  most  of  the  copper 
sprays.  For  use  with  the  sulphur  spraj's  or 
Bordeaux  mixture  containing  a  large  amount  of 
lime,  the  common  Vermorel  or  cyclone  nozzle  is 
rather  too  light  and  the  opening  too  small.  In 
California  a  special  form  of  nozzle  is  in  use  for 
the  application  of  such  sprays  (fig.  3).  This  nozzle 
is  manufactured  in  San  Francisco,  and  may  be 
obtained  from  the  leading  hardware  firms  of  that 
city.  The  nozzle  is  of  the  cyclone  pattern,  but  is  much  larger,  heavier, 
and  stronger  than  the  ordinary'  type  of  cyclone  or  Vermorel.  The  dis- 
charge opening  is  of  sufficient  size  to  allow  of  the  use  of  thick  sprays, 
and  the  discharge  plate  is  heavj^  enough  to  withstand  much  wear  from 
corrosive  fluids.     A  fact  of  prime  importance,  however,  for  the  work 


Fig.  2.— Cyclone 
nozzle,  with 
lateral  dis- 
charge, for 
thin  sprays. 


Fig.  3.— Heavy  cyclone  noz- 
zle, with  oblique  discharge, 
for  thick  sprays. 


GENERAL    ACCESSORIES    FOR  WINTER    SPRAYING. 


169 


being  considered,  is  that  the  nozzle  discharges  the  spray  at  an  angle 
of  al»out  45'^  with  a  lino  leading  directly  from  the  sprayer.  This 
gives  the  nozzle  the  advantages  of  both  the  lateral  and  direct  dis- 
charge. The  work  of  either  of  these  types  (figs.  1,  2,  and  3)  may  l)e 
accomplished  with  this  angular  discharge. 

Makers  of  cyclone  nozzles  of  all  kinds  are  usually  able  to  suppl}'' 
the  discharge  plates  of  the  nozzles  separate!}',  and  this  is  convenient 
for  the  grower,  where  the  original  discharge  plates  have  been  worn 
out.     The  separate  discharge  plates  usually  sell  at  25  cents  each. 


HOSE    AND    EXTENSION"    PIPES. 


Fig.  4. — Wire-extended    suction 
hose. 


Rublier  hose  of  good  quality  is  most  satisfactory  for  aA  kinds  of 
spray  work.  The  strongest  and,  best  hose  will  usually  prove  cheapest 
if  properly  cared  for.  All  hose  should  be 
thoroughly  washed,  both  inside 
and  outside,  at  the  close  of  each 
day's  work,  and  it  should  be 
well  scrubbed,  washed,  and  dried 
when  the  sprav  work  is  com- 
pleted, and  stored  in  a  uniformly 
cool.  dark,  and  medium  dry  place. 

Practice  varies  somewhat  as  to  the  internal  diameter  of 
hose  used.  One-half  inch  is  perhaps  the  most  common  size. 
The  external  diameter  of  the  hose  should  not  be  so  small 
nor  its  flexibility  so  great  that  it  will  easily  kink  and  twist 
upon  itself.  Hose  which  does  this  is  a  constant  source  of 
annoyance,  causing  loss  of  time  and  often  endangering  itself. 
Where  possible,  it  is  best  to  have  all  lines  of  discharge  hose 
leading  from  the  pump  pass  from  the  back  end  of  the  wagon, 
between  two  short  stakes,  one  at  each  corner.  With  such 
an  arrangement  there  is  little  danger  of  its  being  caught  in 
the  wheels  or  run  over  by  them.  Many  lines  of  hose  are 
injured  or  destroyed  in  this  Avay.  The  stakes  at  the  back 
corners  of  the  wagon  also  serve  as  a  means  of  winding  up 
the  hose  preparatory  to  going  to  or  from  the  orchard. 

Couplings  for  connecting  1,  2,  3.  or  4  lines  of  hose  with 
the  pump  may  usually  be  obtained  from  responsible  hard- 
ware firms,  or  through  them  from  the  manufacturers  of  the 
pumps  used.  The  more  common  hose  couplings  are  nearl}' 
always  in  stock  at  such  hardware  houses. 

For  most  pumps  it  is  well  to  supply  wire-extended  suc- 
tion hose  (fig.  4).  Some  stjdes  have  the  spiral  wire  coil 
within  the  interior;  others  have  it  embedded  in  the  rubber. 
When  the  metallic  spiral  is  exposed  to  the  spray  in  the  interior  of 
the  hose  it  should  be  of  brass,  if  possible,  to  enable  it  to  withstand 
the  corrosive  action  of  the  sprays. 


170    PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

Brass  suction  pipe  strainers  for  attachment  to  the  end  of  the  pipe 
may  be  had  of  different  forms.  They  are  necessar}'  when  the  end  of 
the  suction  pipe  is  simply  lowered  into  the  spray  tank  or  when  it  rests 
upon  the  bottom  of  the  tank. 

The  extension  pipes  used  by  different  growers  vary.  Some  adopt 
common  three-eighths  or  one-fourth  inch  iron  tubing,  while  others 
obtain  the  bamboo-covered  extensions,  which  latter  contain  one-fourth 
inch  pipe.  The  essentials  of  an  extension  pipe  are  a  brass  coupling  for 
connecting  the  hose,  a  good  brass  stopcock  for  controlling  the  flow  of 
spra}^,  a  metallic  pipe  of  sufficient  length  (which  should  be  determined 
by  the  height  of  the  trees  to  be  sprayed),  and  upon  the  end  of  the  pipe 
a  thread  and  shoulder  for  the  attachment  of  the  nozzle  and  the  recep- 
tion of  a  washer.  The  ordinary  length  of  extension  pipes  is  8  or  10  feet, 
but  where  trees  are  large  a  12-foot  pipe  may  be  needed.  Either  of 
these  lengths  are  now  obtainable  from  dealers  in  spraying  supplies 
in  the  forni  of  bamboo  extensions  (fig.  5).  There  are  advantages  in 
the  bamboo  extension  pipes  over  uncovered  iron  tubing.  Where  hot 
sulphur  sprays  are  used  the  bamboo  cover  prevents  the  hands  from 
feeling  the  heat,  and  where  cold  sprays  are  applied  in  very  cold  weather 
the  bare,  wet  pipe  is  liable  to  chill  or  even  freeze  to  the  hand.  The 
greater  size  of  the  extension  pipe  which  is  covered  b}'  bamboo  also 
adds  to  the  ease  with  which  the  pipe  may  be  held  and  turned  in  the 
hands. 

PROTECTION    OF   THE   SPRAYER. 

The  nature  of  spray  work  makes  it  unpleasant  for  the  workman,  but 
much  of  this  inconvenience  arises  from  an  incomplete  or  improper 
preparation  for  the  work.  Men  who  would  not  care  to  work  in  a 
rain  storm  without  suitable  covering  are  often  improperl}^  protected 
against  the  similar  or  worse  conditions  prevailing  when  they  are  spray- 
ing. In  the  spraying  of  large  orchards  it  has  been  learned  that  one  of 
the  most  suitable  coverings  for  men  who  are  applying  sprays  is  a  sail- 
or's oilskin  suit  and  sou'wester.  This  covering  is  light,  impervious  to 
wind  and  water,  and  is  not  as  liable  to  crack  as  rubber  clothing.  What- 
ever form  of  head  covering  may  be  chosen  it  should  be  soft,  so  as  not 
to  be  interfered  with  by  limbs,  and  it  should  extend  in  front  to  pro- 
tect the  eyes  and  behind  to  protect  the  neck.  It  is  always  desirable  to 
protect  the  hands  with  long  rubber  gloves,  and  these  can  usually  be 
obtained  from  or  through  druggists.  In  selecting  such  goods,  how- 
ever, it  is  well  to  learn  how  long  they  have  been  held  in  stock  by  the 
dealer,  and  if  they  have  been  kept  for  more  than  a  year  it  is  best  to 
order  new  ones  from  the  manufacturer,  as  such  goods  soon  rot  when 
held  in  stock.  Besides,  new  stock  is  no  more  expensive  than  old,  and 
it  will  frequently  endure  twice  as  much  use.  Numbers  11  or  12  are 
usually  about  the  right  sizes  for  ordinary  hands.     Most  wear  can  be 


SPRAY    PUMPS. 


171 


obtained  from  gloves  which  are  large  for  the  hands,  and  in  such  the 
hands  are  not  as  apt  to  perspire.  Where  ruT)ber  gloves  are  not  obtain- 
able the  hands  may  be  greatly  protected  and  kept  soft  b}-  rubbing  them 
thoroughly,  as  often  as  necessaiy,  with  a  piece  of  beef  suet. 

If  corrosive  sprays  are  to  be  applied,  such  as  the  simple  solution  of 
copper  sulphate,  eau  celeste,  etc.,  it  may  be  found  necessary  to  protect 
the  eyes.  For  this  purpose  ordinary  clear  glass  goggles  may  be  used, 
or  the  sprayer  may  provide  himself  with  mica  goggles  of  large  size, 
such  as  are  worn  in  some  portions  of  the  country  by  men  employed 
about  thrashing  machines.  Both  the  glass  and  the  mica  goggles  may 
be  usually  purchased  through  druggists. 

PUMPS    FOR   VARIOUS    SIZED   ORCHARDS. 


The  selection  of  a  good  spray  pump  is  advisable.  The  difference 
between  the  lirst  cost  of  a  poor  pump  and  that  of  a  good  one  is  little, 
while  the  difference  in  the  ex- 
pense of  spraying  an  orchard 
with  a  poor  and  a  good  pump  is 
apt  to  be  considerable. 

There  are  some  features  which 
every  spray  pump  should  possess. 
It  should  be  furnished  with  an  air 
chamber  for  the  regulation  of  the 
tiow.  and  the  wearing  parts  should 
be  of  brass  or  brass  lined.  It 
should  be  strong  and  work  easily, 
be  supplied  with  means  for  iirm 
attachment,  and  have  capacity 
sufficient  to  maintain  the  recjuired 
pressure  without  undue  rapidity 
of  stroke. 

Pumps  for  small  orchards 
should  be  capable  of  throwing 
two  good  sprat's.  Such  pumps, 
suited  for  attachment  to  the  top 
or  side  of  barrels,  or  to  other  raised  tanks  or  foundations,  are  shown 
in  tigs.  6  and  7.  These  pumps  are  supplied  with  air  chambers  and  are 
of  sulEcient  capacity  for  ordinary  orchard  spraying.  Each  has  a  con- 
nection for  a  small  pipe  leading  down  from  the  discharge  pipe  to  the 
bottom  of  the  barrel  or  tank.  By  opening  a  stopcock  in  the  pipe  a 
stream  may  be  forced  back  into  the  tank  close  to  the  end  of  the  suction 
pipe,  thus  serving  to  free  the  suction  from  deposit  and  to  agitate  the 
spray.  These  pumps  can  be  obtained  with  brass-lined  cylinders. 
The  stroke  is  upward  and  downward.     (See  also  PI.  XXVI.) 


Fig.  (). — Spniy  piimp  fur  iitJu  on  barrt-l  ur  tank. 


172 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


For  orchards  of  medium  to  large  size  it  is  l)etter  to  obtain  more 
powerful  pumps — those  capable  of  throwing  four  strong  sprays.  The 
pimips  shown  in  figs.  8,  9,  and  10  are  admirably  suited  for  this  class 
of  work.  Pumps  of  the  type  shown  in  fig.  8  are  used  in  the  1,600- 
acre  Rio  Bonito  orchard.  In  this  orchard  one  man  pumps  for  four 
men  spraying  (Pis.  XXVII  and  XXVIII).  In  many  portions  of 
California  the  pneumatic  pump,  shown  in  fig.  10,  is  a  favorite.  It  has 
been  used  extensively  in  the  spraying  of  orange  groves  where  the 
trees  are  large  and  where  high  pressure  is  necessary  to  throw  the 
spray  to  their  tops.     The  pumps  shown  in  figs,  8  and  9  have  perpen- 


FiG.  7. — Spray  pump  for  use  on  barrel  or  tank. 

dicular  levers,  thus  avoiding  the  bending  or  stooping  motion  of  the 
operator.  The  levers  of  each  of  the  three  styles  shown  are  long,  and 
both  the  strength  and  capacity  of  the  pump  is  sufficient.  The  style 
of  pumps,  both  for  small  and  large  orchards,  to  which  attention  is  here 
called,  will  be  found  figured  and  listed  in  catalogues  usually  to  be 
found  in  the  hands  of  leading  hardware  dealers. 

Within  the  past  few  vears  leading  orchardists  and  others  have 
tested,  with  varying  success,  the  application  of  difi'erent  motive 
powers  to  the  operation  of  spra}"  pumps.  Steam  and  gasoline  engines 
have  received  most  attention  for  thi-<  ]i-u-poso.     Many  of   the  power 


SPRAY   PUMPS. 


173 


sprayers  as  now  constructed  are  heavy,  cumbersome  affairs,  which 
could  never  l)e  of  practical  value  in  everyday  orchard  work.  Of  the 
machines  or  descriptions  of  the  same  which  have  come  to  the  writer's 
attention,  none  have  thus  far  appeared  better  adapted  to  practical  and 
continuous  orchard  work  than  one  in  use  at  San  Diego.  This  machine 
was  planned  and  constructed  for  Mr.  H.  R.  Gunnis,  of  San  Diego, 
and  has  seen  practical  service  for  several  years.  It  has  been  more 
or  less  changed  and  perfected  from  time  to  time,  such  improvements 
being  made  as  have  seemed  best  from  experience  gained  in  actual  and 
extensive  orchard  work.  This  machine,  as  first  called  to  the  attention 
of  the  writer  l)v  Mr.  Gunnis  in  the  earlv  part  of  July.  1805,  is  illus- 
trated  in  PI.    XXIX.      The 


photograph  from  which  this 
plate  was  made  was  taken 
while  the  machine  was  being- 
used  in  spraving  a  young 
orchard  near  Santa  Barbara. 
In  reference  to  the  changes 
made  since  this  photograph 
was  taken,  Mr.  Gunnis  writes: 

•'The  changes  made  in  the 
machine  since  I  corresponded 
with  you  regarding  it  in  1895 
consist  in  the  addition  of  a 
rotary  supply  pump  and  the 
use  of  a  tender  cart  for  haul- 
ing the  material  to  the  machine 
instead  of  having  to  shut  down 
and  go  to  the  material  every 
time  the  tank  is  emptied."' 
^Ir.  Gunnis  further  says, 
under  date  of  March  10, 
1890:  ''The  machine  is  still 

in  constant  use,  and  I  can  still  say.  as  1  wrote  you  over  three  years 
ago,  that  it  has  developed  no  defects  whatever.  Some  of  the  parts 
wore  out  from  actual  service  and  have  been  replaced,  but  no  changes 
have  been  made  in  its  construction.  *  *  *  The  use  of  the  supply 
pump  and  tender  increases  the  capacity  of  the  outfit  25  or  30  per  cent, 
especially  in  large  orchards.  In  very  small  places  it  can  also  be  used 
economically  by  two  men,  both  spraying,  as  a  good,  steady  team  can 
soon  be  taught  to  move  and  stop  at  the  word.  In  this  case  it  is  not 
necessary  to  use  the  tender." 

While  it  is  believed  that  the  machine  which  Mr.  Gunnis  has  built 
and  operated  is  superior  to  any  other  of  its  class,  I  am  informed  that 
the  gentleman  contemplates  still  further  improvements.     In  regard 


^pray  pnmi)  for  general  orehnrd  work,  upright 


174 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


to  these  changes  Mr.  Gunuis  says  that  he  is  now  building  from  nis 
own  designs,  and  has  almost  completed,  a  small  gasoline  engine  of  3  to 
4  horsepower,  weighing  less  than  200  pounds.  This  engine  is  intended 
for  use  with  a  spraying  machine  embodying'  all  the  features  of  his  old 
apparatus,  but  lighter  and  more  compact.  He  also  has  plans  under 
way  for  a  self-propelling  machine,  in  ^vhich  the  extra  power  required 
will  not  cost  half  of  what  it  does  to  feed  a  team,  and  which  can  be 
much  more  easily  controlled. 


Fig.  9. — Spray  pump  for  geufral  orchard  -work,  upright  lever. 

PI.  XXX  shows  the  right  and  left  sides  of  Mr.   Gunnis  s  sprayer 
as  it  appeared  after  the  addition  of  the  rotary-  pump  for  tilling  the 
spray  tank.     A  detailed  description  of  this  machine  was  prepared  by 
Gunnis  and  published  in  the  Yearbook  of  the  Department  for 


Mr, 


1896  (pages  73  and  74),  in  an  article  by  L.  O.  Howard,  on  the  use  of 
steam  apparatus  for  spraying.  Those  wishing  more  complete  details 
may  refer  to  ]\Ir.  Gunnis  direct,  to  whom  the  writer  is  indebted  for 
the  illustrations  and  facts  here  giyen. 


THE    APPLICATION'    OF    SPRAYS. 


175 


SPK.VYINC;    TANKS. 

A  great  variet\^  of  forms  and  sizes  of  spray  tanks  are  in  use.  For 
small  orchards,  scarcely'  anything  better  could  be  desired  than  large 
oak  barrels  holding  GO  to  80  gallons.  These  may  be  swung  upon 
wheels  separately  if  desired,  but  the  most  convenient  way  is  to  place 
them  tirmly  in  a  one  or  two  horse  wagon.  Large  tanks,  well  hooped, 
are  also  very  suitable  for  large  orchards.  Casks  of  this  kind,  holding 
300  gallons,  may  easily  be  placed  in  the  bottom  of  a  two-horse  wagon, 
leaving  abundant  room  for  placing  and  operating  the  heavy  hand 
pump.  Such  casks  are  shown  in  Pis.  XXVII  and  XXVIII.  The 
manner  of  securing  the  tank  by  placing  side  timbers  inside  of  the 
wagon  bolsters  is  shown  in  PI.  XXII, 
as  is  also  the  stirring  stick  which 
projects  from  a  square  hole  in  the 
top  of  the  cask. 

Rectang-ular  plank  tanks  are  used 
by  some,  but  it  is  generally  found 
more  difficult  to  keep  them  from 
leaking  than  in  the  case  of  casks, 
where  the  hoops  may  be  tightened 
at  will.  Numerous  spray  carts,  bar- 
rel attachments,  etc..  are  illustrated 
in  E.  G.  Lodeman's  Avork  on  The 
Spraying  of  Plants. 

The  use  of  iron  tanks  is  rare,  and 
is  hardly  to  be  advised  for  general 
spray  work,  owing  to  the  corrosive 
action  of  many  sprays.  For  special 
sprays,  as  the  kerosene  emulsion, 
such  tanks  may,  however,  be  safely 
employed. 

All  spray  tanks  should  be  arranged 
in  such  a  manner  as  to  be  easily 
cleaned,  especialh'  where  Bordeaux  mixture  or  the  sulphur  sprays  are 
to  be  used,  and  the}'  should  be  provided  with  some  means  for  stirring 
or  agitating  the  spray.  The  entrance  to  all  suction  pipes  should  be 
guarded  with  tine  brass  wire  screen.  It  is  well  to  wash  the  tanks  out 
thorouohlv  at  least  once  a  dav. 


Fig  10. — Pneumatic  pump  for  general 
spraying. 


APPLYING  WINTKR  SPRAYS  FOR  CURL. 

A  stud}'  of  the  many  experiments  conducted  ])y  the  growers  and 
described  in  this  bulletin  will  give  much  infonuation  relative  to  the 
proper  time  for  applying  sprays  for  the  control  of  curl.     A  presenta 
tion  of  a  few  general  principles  involved  may,  however,  be  properly 
made  in  this  place. 


176    PEACH  LEAF  CURL:  ITS  MATURE  AXD  TREATMENT. 


THE    TIME    FOR    WINTER    SPRAYING. 


The  proper  time  for  the  application  of  winter  sprays  for  the  control 
of  peach  leaf  curl  depends  very  largely  upon  the  conditions  of  climate, 
season,  and  situation  of  the  orchard.  The  object  to  be  attained  is  to 
prevent  the  fungus  from  infecting  the  lirst  growth  of  spring.  It  has 
become  apparent  from  the  man}'  and  wideh"  separated  experiments 
which  are  here  described  that  nearly  if  not  all  this  infection  result, 
from  the  spores  of  the  fungus,  which  are  present  upon  the  tree  and 
not.  as  formerly  supposed,  from  a  perennial  mycelium,  and  it  natui 
ally  follows  that  these  spores  are  to  be  destroj^ed  or  their  germination 
prevented  if  the  new  growth  is  to  be  kept  exempt  from  curl.  When 
a  spore  is  about  to  germinate  or  has  just  begun  to  germinate,  its  mem- 
branes are  most  tender  and  susceptible  to  fungicides.  That  most  of 
the  spores  of  JExoascus  deformans  enter  upon  the  stage  of  germina- 
tion at  or  about  the  time  of  the  pushing  of  the  first  leaf  buds  in  the 
spring  admits  of  little  doubt.  That  is  the  time  when  the  tissues  of  the 
peach  leaf  are  most  tender,  imd  when  their  infection  by  curl  is  actually 
known  to  take  place. 

The  preceding  facts  indicate  that  the  time  when  the  fungicide  is  apt 
to  do  the  greatest  good  is  just  before  or  at  the  time  of  the  earliest  push- 
ing of  the  peach  leaf  buds.  The  spray  should  be  everywhere  present 
upon  the  trees  just  prior  to  the  beginning  of  growth.  To  obtain  this 
object  it  should  be  applied  from  one  to  three  weeks  before  growth 
begins.  This  time  may  usuall}'  be  determined  l\y  carefully  watch- 
ing the  fruit  buds,  which  show  signs  of  swelling  some  time  before 
thev  open.  "When  thev  first  begin  to  swell,  the  sprav  mav  be  at  once 
applied  (Pis.  XXIII,  XX lY,  and  XXV). 

This  plan  relates  to  regions  of  moderate  rainfall,  where  a  single 
thorough  spraying,  with  sprays  sutficiently  strong  and  active,  will 
prove  sufficient.  In  regions  of  heavy  precipitation  more  spray  should 
be  applied  to  the  trees.  It  should  be  stronger  and  have  greater  adher- 
ing qualities,  or  else  more  than  one  spraying  during  the  winter  will  be 
required  to  give  the  best  results.  If  two  sprayings  are  given,  it  is 
better  to  apply  both  to  the  dormant  tree  than  to  delay  the  second 
treatment  till  the  leaf  buds  have  opened  The  first  spraying  may  be 
given  in  the  fall  or  a  few  weeks  before  the  second. 


THE    MAXXER    OF    APPLYING    WINTER    SPRAYS. 


The  source  of  infection  of  the  spring  foliag  of  the  peach  by  the 
fungus  of  leaf  curl  is  local — i.  e.,  it  is  to  be  found  upon  every  portion 
of  the  tree.  This  fact  is  sufficient  to  shov  that  any  portions  of  the 
tree  not  reached  by  the  spra}'  will  be  as  subjec  to  the  disease  as  if  no 
spraying  had  been  done.  It  thus  becomes  apparent  that  ver}-  thorough 
work  is  essential  to  the  general  control  of  the  disease  upon  the  tree. 


DESCRIPTION  OF  PLAT?:  XXIII. 

This  plate  shows  tlie  condition  of  the  trees  in  the  experiment  block  of  the  liio 
Bonito  orchard  at  the  close  of  the  spray  work  in  the  spring  of  1895.  The  row  of 
trees  at  the  left  has  been  sprayed;  that  at  the  right  has  been  left  unsprayed  for  com- 
parison. The  first  10  trees  on  the  left  have  been  treated  with  a  spray  containing  a 
moderate  amount  of  lime;  the  second  10  in  the  same  row  were  treated  with  a  spray 
containing  more  lime,  and  they  are  much  whiter  than  those  in  the  foreground. 
Each  row  of  10  sprayed  trees  on  the  left  and  the  corresponding  row  of  10  unsprayed 
trees  on  the  right  constituted  an  experiment.  The  uniformity  in  tlie  size  of  the  trees 
in  these  experiments  is  here  shown  to  advantage.  It  should  be  noted  that  the  buds 
are  still  closed,  while  tiie  spraying  is  completed. 


Bull.  20,  Div.  Veg.  Phys.  &  Patn.,  U,  S.  Dept.  of  Agriculture. 


Plate  XXIII. 


*%r 


V^'l 


<-'/ 


DESCRIPTION  OF  PLATi:  XXIV. 

A  portion  of  the  Lovell  trees  in  the  Rio  Bonito  orchard  left  unpruned  until  too 
late  to  spray,  many  of  the  flowers  being  already  open.  This  plate  should  be  com- 
pared with  PI.  XXV,  which  shows  how  the  orchard  should  be  pruned  before  spray- 
ing, and  also  with  PI.  XXIII,  which  shows  how  far  l)ud  development  may  ordinarilj- 
be  allowed  to  advance  in  the  spring  up  to  the  time  the  s})ray  work  is  completed. 


Bull.  20,  Div.  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XXIV. 


5    H 

~    o 
T     o 


DESCRIPTION  OF  PLATE  XXV. 

A  properly  pruned  portion  of  the  Rio  Bonito  orchard,  which  has  developed  too 
far  for  the  best  results  of  spraying.  Spraying  should  be  completed  by  the  time  the 
buds  have  developed  as  far  as  those  shown  in  PI.  XXIII. 


Bull.  20.  Div.  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XXV. 


SPRAYING    WHERE    SEVERAL    DISEASES    ARE    PRESENT.        177 

Thorough  .spray  work  requires  that  the  sprays  be  applied  in  as  cahn 
weather  as  possible.  Wind  greatly  retards  and  lowers  the  class  of 
work  done.  Sprays  should  likewise  not  l)e  applied  when  the  twigs  or 
limbs  of  the  trees  are  covered  by  frost,  snow,  or  sleet,  or  by  the  water 
of  rains,  dew,  or  heavy  fogs.  To  avoid  the  presence  of  hanging  drops 
of  dew  upon  the  limbs,  it  is  frecjuently  necessary  to  delay  spraying 
until  late  in  the  morning.  Such  delay  is  preferable  to  the  application 
of  spray  to  the  dripping  trees.  When  the  twigs  are  dry  the  sprav 
dries  where  it  strikes,  and  succeeding  dews  or  showers,  if  the  latter 
are  not  too  heavy,  will  not  wash  oil'  the  spray  to  a  very  injurious 
extent. 

If  the  sprayer  is  provided  with  suital)le  extension  pipe  and  nozzle 
with  lateral  discharge,  the  work  of  spraying  peach  trees  of  ordinary 
size  may  be  rapidly  and  easily  done.  The  cone  of  spray  is  first  turned 
upward  under  the  l)ase  of  one  of  the  main  limbs  of  the  tree  and  the 
pipe  moved  so  that  the  spray  passes  outward  toward  the  end  of  the 
limb,  spraying  the  entire  under  surface  of  the  limb  from  base  to  tip. 
The  sides  and  top  of  the  liml)  are  now  sprayed,  together  with  all  of 
its  terminal  branches  and  twigs.  Each  main  limb  of  the  tree  is  treated 
in  like  manner,  the  sprayer  passing  about  the  tree  as  the  work  is  com- 
pleted. The  habit  of  actively  moving  the  nozzle  back  and  forth  while 
at  work  will  soon  be  acquired  b}^  the  workman  desirous  of  doing  good 
work,  and  hy  this  means  the  most  uniform  spraying  is  accomplished. 

SPRAYING   WHERE    OTHER    DISEASES   ARE    PRESENT   WITH   CURL. 

There  are  many  peach  diseases  which  may  coexist  upon  the  tree 
with  curl.  Many  of  these  are  amenable,  in  whole  or  in  part,  to  treat- 
ment adapted  to  the  control  of  curl,  but  in  some  cases  where  two  or 
more  are  present  it  ma}'  be  advisable  to  make  slight  alterations  in  the 
treatment.  The  following  notes  on  some  of  the  more  common  dis- 
eases may  prove  of  value. 

PRUNE  RUST  OX  THE  PEACH  {Puccinia  jminl  Fers.) . 

-  It  is  a  fact  which  does  not  appear  to  be  generally  known  that  prune 
rust  infests  the  tender  branches  of  the  peach  as  well  as  its  leaves. 
This  has  been  found  especially  true  in  young  trees.  S\)oyq-  clusters  are 
found  upon  the  young  shoots  before  growth  begins  in  the  spring, 
showing  that  the  disease  winters  over  by  means  of  spores  produced 
upon  and  remaining  attached  to  the  branches,  as  well  as  by  the  spores 
produced  upon  the  leaves  and  scattered  o\er  the  tree.  Where  the 
trees  are  suffering  from  rust  it  is  therefore  apparent  that  a  thorough 
winter  treatment  is  required  to  clean  the  tree  and  prevent  the  spring 
infection,  hence  such  spraying  is  reconunended  for  the  control  of  both 
curl  and  rust,  though  the  full  control  of  th(^  latter  disease  is  very 
19093— No.  20 12 


178    PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 

difficult  and  will,  at  best,  be  necessarily  followed  by  several  summer 
treatments.  There  can  be  little  doubt,  however,  that  a  thorough 
winter  spraying  will  prevent  a  greater  portion  of  the  injurj^  from  rust 
than  an}^  single  spraying  applied  at  a  later  date,  as  it  gives  a  practi- 
cally clean  tree  at  the  opening  of  the  season  of  growth.  Winter 
sprays  for  the  control  of  rust  must  be  strong;  but  summer  sprays  if 
strong  should  be  positively  neutral  and  noncorrosive,  as  peach  foliage 
is  exceedingly  tender. 

MILDEW  OF  THE  PEACH   {Poclosplixra  oxyacantlix  De  B.) . 

Peach  mildew  is  widely  distributed  in  the  United  States  and  in 
Europe.  The  fungus  causing  it  attacks  the  leaves,  fruit,  and  tender 
branches  in  the  early  part  of  the  summer.  The  branches  serve  for 
the  wintering  over  of  the  spores,  thus  aiding  in  supplying  the  source 
of  spring  infection.  Winter  treatment  of  the  trees,  with  either  the 
copper  or  sulphur  sprays,  will  largely  limit  this  spring  infection, 
but  later  treatment  with  weak  spraj^s  will  often  be  necessary  for  full 
control. 

BROWN  ROT  OF  THE  PEACH  {MonUia  fructigena  FeTS.) . 

Brown  rot  of  the  peach  has  become  one  of  the  worst  fungous  dis- 
eases of  the  peach  over  large  portions  of  the  United  States.  It  is 
quite  general  throughout  most  peach-growing  sections  of  the  East, 
and  has  become  well  established  in  the  Pacific  Northwest.  It  has  been 
shown  by  Erwin  F.  Smith  that  the  fungus  winters  over  in  the  diseased 
branches  and  in  the  dried  fruit  adhering  to  the  tree.  These  facts 
point  to  a  thorough  winter  spraying  with  active  fungicides  as  one  of 
the  first  steps  required  in  its  treatment.  Summer  sprayings  will  also 
be  required,  and  even  when  thoroughly  followed  up,  the  disease  will 
prove  hard  to  control.  Too  much  stress  can  not  be  laid,  however, 
upon  the  necessity  of  disinfecting  the  dormant  tree  as  perfectly  as 
possible  by  thorough  winter  treatment. 

BLACK  SPOT  OF  THE  PEACH  {Cladosj^orium  carpophihuu  Thiim.y . 

This  disease,  which  produces  black  spots  upon  the  peach,  is  well 
known  in  many  portions  of  the  United  States  and  in  Europe,  and  in 
the  East  and  South,  especially  in  Texas,  it  has  become  quite  trouble- 
some. In  some  parts  of  Europe  it  has  been  known  as  a  true  epiphy- 
totic.  Whether  this  Cladosporium  infes^the_  branches  the  writer 
can  not  say,  but  it  appears  not  improbjjjle  that  such  istrue,  or  in  any 
case  that  the  spores  probably  find  winter  lodgment  upon_the_tree  itself. 
Black  spot  has  been  controlled  in  Texas  by  the  use  of  the  copper 
sprays,  and  there  seems  no  reason-  to  doubt  that  the  winter  treatment 
of  the  infected  trees  would  largely  tend  to  disinfect  them  and  materi- 
ally reduce  tl^e  summer  development  of  thejdisease. 


SPRAYING    WHERP:    SEVERAL    DISEASES    ARE    PRESENT.        179 

•\VINTKK    ULIGIIT   OF    THE    I'EACH    AND     OTUEK    SPOT   AND    SIIOT-IIOLE     DISEASES,    SUCH    AS 

Pln/Husticia  clrcuiiD^cixxd  kerk.,  Ccrvospora  circumscissa  axcc. ,  etc. 

In  the  Northwest,  on  the  riieitic  c-oast,  there  are  several  diseases  of 
the  peach  not  generally  known  throughout  the  East,  and  also  several 
other  diseases  connnon  to  both  sections  of  the  country.  These  troubles 
are  genoriilly  known  as  leaf  spot  or  shot-hole  diseases.  One  very 
widely  distrilmted  disease  is  that  pi'oduced  by  Cercosjx/ra  ciroum^<dssa 
Sacc,  but  one  of  the  most  troublesome  diseases  of  this  class  that 
occurs  in  California  and  Oregon,  is  induced  by  a  fungus  not  yet  fully 
studied,  which  infests  the  tender  and  bearing  branches  and  appears  to 
begin  its  vegetative  activity  some  time  })rior  to  the  blooming  of  the 
tree  in  the  spring.  On  account  of  the  hal)it  of  the  fungus  to  grow  in 
the  dormant  or  semidormant  bninches  of  the  tree,  the  disease  is  termed 
by  the  writer  the  vunter  hlight  of  the  peach.  It  is  one  of  those  dis- 
eases which  destroys  the  most  valuable  young  growth  of  the  tree,  i.  e., 
the  shoots  which  are  low  and  suited  to  the  production  of  the  finest 
fruit.  This  disease,  in  common  with  another  quite  prevalent  on  the 
Pacific  coast  and  which  is  probably  induced  by  a  Corynemn.,  does 
most  damage  in  the  more  humid  localities.  Both  do  their  more  serious 
work  so  early,  as  is  also  true  of  peach  leaf  curl,  that  summer  spra^dng 
would  have  but  little  efi'ect  toward  their  control.  Both  induce  gum- 
mosis  of  the  affected  branches,  as  is  true  of  the  action  of  many  fungi, 
and  is  a  well-marked  i-esult  of  the  presence  of  Corynenm  hyn'hickil 
Ond.  Winter  ])light  has  already  been  successfully  treated  with  the 
winter  spra3^s,  and  it  is  believed  that  such  sprajang  is  sufficient  for  its 
control,  pro\aded  the  work  be  done  thoroughl}'^  and  repeated  each  year. 

There  is  no  doubt  that  the  winter  treatment  of  the  peach  for  curl  is 
properly  and  essentially  the  first  step  for  the  control  of  an}-  of  the 
above-mentioned  diseases.  Too  much  can  not  be  said  in  favor  of  this 
treatment,  which  disinfects  the  trees  before  vegetative  growth  begins. 
The  striking  thoroughness  of  such  disinfection  work  may  be  seen 
from  the  records  given  below. 

SOOTY    MOl.D    OK    THE    PEACH. 

When  the  Department  spraying  experiments  began  in  the  Rio 
Bonito  orchard,  there  was  everywhere  present  on  the  trunks,  inner 
limbs,  and  older  bark  of  the  experiment  trees  a  fungous  ''smut,"  or 
"sooty  mold,"  giving  the  bark  a  black  appearance  when  closely 
examined.  Of  the  58  rows  included  in  this  ])lock,  35  were  sprayed, 
as  before  stated,  prior  to  March  10,  and  23  left  unspriiyed  for  com- 
parison. On  August  10,  5  months  after  the  spraying  was  completed, 
all  1)ut  \  rows  were  examined  for  the  presence  of  soot}'  mold,  with  the 
following  result: 

Sprayed  rows  showing  no  sooty  mold  August  10:  Nos.  1,  3,  (>,  7,  10, 
12, 13, 15, 16, 18, 19,  21,  22,  25,  27^  28,  33,  35,  30,  38,  39,  41,  45, 47,  48,  50, 
51,  54,  h'6^  and  57 — total,  30  rows. 


180    PEACH  LEAF  CURL!  ITS  NATURE  AND  TREATMENT. 

Sprayed  rows  showino-  a  trace  of  sooty  mold:  Nos.  42  and  -44:  (sul- 
phide of  potassiuiii  was  applied  to  row  42  and  simple  milk  of  lime  to 
row  44) — total,  2  rows. 

Unsprayed  rows  showing'  the  presence  of  sooty  mold  upon  the  trees 
August  10:  Nos.  2,  5,  8,  11,  14,  IT,  20,  23,  26,  21),  34,  87,  40,  43,  46, 
49,  52,  55,  and  58 — total,  19  rows. 

Unsprayed  trees  showing  no  sooty  mold,  none. 

Rows  sprayed  in  1894,  but  not  spra^'ed  in  1895:  No.  4.  no  mold 
apparent;  No.  24,  some  mold  present;  No.  53,  a  little  mold  present — 
total,  3  rows. 

Rows  for  which  no  notes  on  sooty  mold  were  obtained:  Nos.  9,  30, 
31,  and  32 — total,  4  rows. 

The  above  notes  show  that  records  of  the  soot}'  mold  were  obtained 
from  32  rows  of  sprayed  trees  5  months  after  treatment.  Of  these, 
80  rows  showed  no  sooty  mold,  while  2  showed  a  very  little.  Neither 
of-  these  exceptional  rows  was  sprayed  with  a  generally  recognized 
fungicide.  On  the  other  hand,  of  the  19  unsprayed  rows  examined, 
all  showed  sooty  mold.  The  record  for  rows  sprayed  in  1894  but  left 
unsprayed  in  1895,  shows  that  the  trees  had  but  little  mold  upon  them 
17  months  after  spraying. 

The  preceding  facts  show  the  disinfecting  value  of  a  single  winter 
spraying,  even  where  the  whole  tree  surface  is  covered  with  fungous 
mycelium  and  spores. 

ANIMAL    PARASITES    OF   THE    PEACH    TREE. 

Among  the  insect  pests  of  the  peach  tree  now  prevalent  in  many 
parts  of  the  United  States,  the  San  Jose  scale  (Asjjuliotu-s  per/u'cio-sm 
Com.)  is  probably  the  most  injurious.  This  pest,  as  is  already-  well 
known  on  the  Pacific  coast,  can  be  controlled  by  winter  spraying  with 
the  sulphur  sprays  considered  in  this  bulletin.  Where  the  insect  is 
known  to  be  present,  the  strongest  of  these  sprays  described  should  be 
used,  and  it  would  be  well  to  apply  it  somewhat  earlier  in  the  spring 
than  where  weaker  sprays  are  used. 

All  leaf -eating  insects  depositing  winter  eggs  upon  the  tree  ma}" 
be  largely  controlled  by  the  winter  use  of  sulphur  sprays.  There 
is  also  a  mite  {Phytoptus  sp.  ?)  infesting  the  peach  leaves  in  Califor- 
nia, which  (the  writer  believes  may  be  destroyed  in  this  manner, 
from  the  fait  that  experiments  conducted  in  1895  in  the  Sacramento 
Valley  showed  that  the  same  line  of  treatment  is  efl'ective  in  the 
destruction  of  a  related  mite  {PJtytoj^tus  j>yi'l  Sor.)  upon  the  pear. 

Mr.  William  N.  Runyon,  of  Courtland,  Cal.,  makes  the  following 
statement  respecting  the  peach  moth,  which  may  also  prove  of  value 
to  growers  suffering  from  this  pest:  "'" Incidentall}'  I  would  state  that 
experience  shows  that  peach  trees  sprayed  with  lime,  sulphur,  and 
salt  are  not  diibject  to  the  attacks  of  the  larva  of  the  peach  moth. 
Some  growers  Vlaim  a  saving  of  90  per  cent  of  affected  fruit." 


CHAPTER  X. 

NATURE   AND   SOURCE   OF   THE   SPRAYING   MATERIALS   USED. 

Tlu'  following  notes  on  the  chemicals  for  sprays  are  presented  for 
the  general  information  of  the  fruit  grower.  The  facts  given  are 
those  which  every  sprayer  should  understand. 

Spraying  is  frequently  retarded  or  prevented  owing  to  a  want  of 
information  relative  to  the  nature,  sources  of  suppl}^,  or  true  value  of 
the  chemicals  required.  A  grower  uninformed  upon  the  last-named 
point  is  often  at  the  mercy  of  local  druggists  or  other  dealers.  For 
example,  copper  carbonate  can  be  made  by  the  grower  himself  at  from 
13  to  14  cents  per  pound,  and  ammonia  of  26°  strength  may  be  pur- 
chased at  al)out  (>()  cents  per  gallon,  w^hile  local  prices  have  been 
known  to  range  as  high  as  $1  per  pound  for  copper  carbonate  and 
^1.50  per  gallon  for  ammonia,  which  makes  it  impossible  to  undertake 
sprav  work.  The  writer  has  found  the  same  conditions  prevailing  in 
respect  to  prices  for  sulphur,  which  is  used  very  largelj  in  the  sulphur 
sprays  and  for  the  treatment  of  mildew.  In  some  cases  the  prices 
asked  by  dealers  in  the  East  have  been  100  or  500  per  cent  higher 
than  growers  have  for  years  been  paving  in  California.  It  can 
not  be  expected  that  the  sulphur  sprays  will  be  generally  used  in  the 
East  under  such  conditions. 

copi'p^R  SULPHATE  (fomuda  CuS0^5H.,0). 

Of  all  fungicides  thus  far  known,  copper  sulphate  is  the  most 
important.  It  is  conmioid}'  known  as  blue  vitriol  or  ])luestone  in  the 
United  States.  Its  foreign  names  are  largely  equivalents  of  these 
terms,  although  the  Germans  also  apply  th(>  name  of  copper  vitriol 
{Kupfei'rlft'iol). 

When  pure,  copper  sulphate  crystallizes  in  large.  Hue,  triclinic 
prisms.  It  contains  about  25.3  per  cent  of  copper,  and  dissolves  in 
four  i)arts  of  cold  water  and  two  parts  of  boiling  water. 

The  presence  of  iron  is  indicated  by  a  greenish  color  of  the  crystals 
or  at  the  surface  of  a  watery  solution  when  exposed  ro  the  air.  A 
solution  of  pure  copper  sulphate  should  be  blue.  The  presence  of  a 
small  amount  of  iron,  which  commonly  occurs  when  copper  sulphate 
is  manufactured  ns  a  by-product  in  modern  smelting  works,  does  not 
necessarily  detract  from  its  value  as  a  fungicide,  while  this  by-product 

181 


182  PEACH    LEAF    CUKL:    ITS    NATURE    AND    TREATMENT. 

may  often  be  purchased  at  a  somewhat  lower  figure  than  a  purer 
article.  Spra^ying  tests  have  been  made  b}'  the  writer  for  the  com- 
paiison  of  pure  commercial  bluestone  with  that  obtained  as  a  by-prod- 
uct of  smelting  works,  and  which  contained  a  considerable  amount  of 
iron,  and  the  results  showed  that  the  latter  article  contained  fully  as 
great  fungicidal  value  as  the  former. 

The  manufacture  of  copper  sulphate  is  carried  on  at  a  considerable 
number  of  estal^lishments  in  the  United  States,  and  various  processes 
are  followed.  A  large  amount  of  this  chemical  is  also  imported, 
chiefly  from  England. 

Bluestone  is  prepared  l:)y  dissolving  cupric  oxide  in  sulphuric  acid, 
or  by  oxidizing  the  sulphide  of  copper,  the  latter  being  the  cheaper 
process.  Mr.  Alfred  Rapp,  a  gentleman  who  has  enjoyed  a  wide 
experience,  has  kindly  supplied  the  following  facts  respecting  the 
manufacture  of  copper  sulphate  by  a  leading  smelting  firm  of  the 
Pacific  coast.  He  states  that  the  copper  is  mainly  derived  from  mattes 
produced  in  the  blast  furnaces,  and,  secondlj^,  from  an  acid  solution 
of  sulphate  of  copper  resulting  from  the  precipitation  of  silver  by 
metallic  copper  out  of  a  sulphate  solution.  To  bring  the  copper  in  the 
difl^erent  mattes  in  solution  they  are  first  crushed  and  pulverized  to 
about  one-thirty-second  of  an  inch  or  finer,  and  subjected  to  a  roasting 
process  by  which  the  sulphur  is  nearly  all  oxidized.  The  roasted 
matte  contains  the  copper  as  oxide  and  partly  as  sulphate,  with  a  small 
amount  still  as  sulphide.  This  material  is  pulverized  once  more  and 
fed  into  lead-lined  leaching  tanks,  where  the  acid  copper  sulphate 
solution  is  added,  and,  if  necessary,  sulphuric  acid.  The  whole  mass 
is  heated  by  steam  running  through  lead  pipes.  The  copper  oxide 
and  the  copper  sulphate  in  the  roast  is  thus  brought  in  solution  as  a 
sulphate.  About  80  per  cent  of  the  copper  contained  in  the  m.attes  is 
thus  leached  out.  The  resulting  solution,  of  course,  is  not  a  neutral 
one,  but  still  contains  an  excess  of  free  sulphuric  acid.  This  solution 
is  transferred  to  other  lead-lined  tanks,  containing,  suspended  from 
wooden  sticks,  strips  of  lead  about  3  inches  wide,  the  central  portion 
of  which  is  bent  downward  l>etween  the  sticks  so  as  to  form  a  loop, 
which  is  held  b}-  the  ends  of  the  lead  strips  being  bent  over  the  sticks. 
The  copper  sulphate  when  run  down  to  these  crystallizing  tanks  is 
about  36^  to  44'^  B.  During  the  cooling  process,  which  takes  about 
four  to  seven  days,  the  copper  sulphate,  or  rather  part  of  it,  separates 
out  of  the  solution  as  blue  crystals,  which  are  deposited  upon  the 
strips  of  lead.  '  These  crystals  are  dried  and  packed  in  barrels  ready 
for  the  market).  This,  Mr.  Rapp  adds,  is  the  general  way  in  which 
bluestone  is  maae  the  world  over,  except  that  they  have  at  the  works 
considered,  in  audition  to  the  copper  in  the  mattes,  the  acid  copper 
sulphate  soiutiori  from  a  silver  refinery. 


NATURE    AND    SOURCE    OF    SPRAYING    MATERIALS.  183 

Water  drain ino^  from  copper  iiiinos  sometimes  carries  copper  sulphate 
in  solution,  in  which  case  the  crystals  are  procured  hy  evaporatino-  the 
excess  of  water.  Barrels  of  coppej-  sulphate  weigh  from  300  to  000 
pounds. 

The  mamifa('turer''s  price  of  copper  sidphate  will  depend  largel}'^ 
upon  the  price  of  copper  and  sulphuric  acid — two  leading  constituents, 
as  they  are  sold  in  the  market — and  upon  supply  and  demand.  The 
cost  to  the  manufacturer  will  not,  however,  necessarily  depend  upon 
the  market  value  of  copper  and  acid,  for  one  or  both  may  be  ol)tained 
by  him  as  by-products  in  other  regular  and  profitable  lines  of  manu- 
facture, such  as  the  smelting  of  gold  and  silver  ores,  etc.^ 

COPPER    CARBONATE. 

Chopper  carbonate  as  usually  prepared  shows  the  following  formula: 
CuCOg.  CuHjO^.  It  is  widel}'  used  in  the  preparation  of  ammoni- 
acal  copper  carbonate  sprays,  and  is  especially  well  adapted  to  the 
treatment  of  maturing  fn^it  where  sul)ject  to  fungous  diseases.  As 
commonl}"  sold  on  the  market,  the  carbonate  of  copper  is  green  and 
finely  granular  or  powdery.  It  contains  about  57.4:  per  cent  of  cop- 
per. Native  minerals  of  similar  composition  occur,  such  as  malachite 
and  azurite. 

Copper  carbonate  is  manufactured  by  a  number  of  firms  in  the 
United  States,  but  much  less  extensively  than  the  sulphate.  In  most 
cases  it  is  prepared  b}^  adding  to  a  solution  of  copper  sulphate  an 
excess  of  sodium  carbonate  (sal  soda)  in  solution.  This  gives  a  floc- 
culent  mixture  of  pale  blue  color,  afterwards  changing  to  green. 
Heating  makes  the  precipitate  more  granular. 

Owing  to  the  difficulty  of  obtaining  carbonate  of  copper  in  smaller 
towns,  as  well  as  the  high  price  usually  charged  for  it,  the  Depart- 
ment has  usuall}'  recommended  that  the  fruit  growers  prepare  it. 
The  following  instructions  for  this  work  were  published  by  the  writer 
in  a  circular  sent  to  the  peach  g-rowers  of  the  country  in  18!'-1— 95:  In 
a  barrel  dissolve  B  pounds  of   copper  sulphate  in  4  gallons  of  hot 

'  Owing  to  the  somewhat  enhanced  value  of  copper  at  this  time  (March,  1899) ,  the 
wholesalepriceof  coi)per8ulphatehasadvanced.  San  Francisco  producers  quote  copper 
sulphate  in  barrels,  f.  o.  b.,  at  5\  cents,  and  carload  lots  at  5  cents  per  ]iound;  Omaha 
((notations  are,  by  the  ton  or  carload,  5^  cents;  one  New  York  firm  (juotes  5|  cents 
l)y  the  l)arrel  or  ton  and  .5^  cents  by  the  carload,  and  a  second  firm  quotes  6  cents  by 
tbe  barrel,  5^%  cents  by  the  ton,  and  5|  cents  by  the  carload;  Denver  quotations  are 
6  cents  by  the  barrel,  5|  cents  by  the  ton,  and  .5.1  cents  by  the  carload;  Cleveland 
quotes  6  cents  per  pound  in  any  (|uantity;  one  Philadelphia  firm  quotes  6  cents  by 
the  barrel,  5|  cents  l)y  the  ton,  and  5f  cents  by  the  carload,  and  a  second  firm  quotes 
.5|  cents  by  the  barrel,  5^  cents  by  the  ton,  and  5}  cents  by  the  carload;  Baltimore 
quotes  5|  cents  by  the  barrel,  5^  cents  by  the  ton,  and  b^  cents  by  the  carload;  Great 
Falls,  Mont.,  quotes  4|  cents  per  pound  in  carload  lots  and  5  cents  per  pound  for  less 
than  carload  lots,  etc. 


184  PEACH    LEAF    CUKL:    ITS    NATURE    A"ND    TREATMENT. 

water.  In  another  wooden  vessel  dissolve  7  pounds  of  washing 
or  sal  soda,  in  2  gallons  of  hot  water.  The  soda  should  be  clear 
(translucent),  and  not  white  and  powdery,  as  it  appears  when  air  slaked. 
When  cool,  pour  the  soda  solution  slowly  into  the  copper  solution. 
As  soon  as  bubbles  cease  to  rise  fill  the  l)arrel  with  water,  stir  thor- 
oughly, and  allow  the  mixture  to  stand  over  night  to  settle.  The 
next  day  siphon  off  all  the  clear  liquid  from  the  top  with  a  piece  of 
hose,  fill  the  barrel  with  water,  stir  thoroughh^,  and  allow  it  to  stand  a 
second  night.  Siphon  off  the  clear  liquid  the  second  day,  fill  the  bar- 
rel with  water,  stir,  and  siphon  off'  the  clear  liquid  once  more  the 
third  day.  Now  pour  the  wet  sediment  from  the  barrel  into  a  crock 
or  other  earthen  dish,  strain  out  the  excess  of  water  through  a  cloth, 
and  dry  slowly  in  an  open  oven,  stirring  occasionallv,  if  necessar}^  to 
prevent  overheating.  Prepared  in  this  manner  there  should  be 
obtained,  if  none  of  the  sediment  in  the  barrel  be  lost,  about  2.65 
pounds  of  carbonate  of  copper. 

Owing  most  probably  to  the  comparatively  limited  sale  of  carbonate 
of  copper,  the  market  price  has  been  and  still  remains  too  high.  It 
can  rarely  be  obtained  for  less  than  30  to  40  cents  per  pound,  which  is 
from  two  to  three  times  the  cost  to  the  grower  when  it  is  prepared  at 
home.  This  condition  reacts  upon  the  manufacturer  by  causing 
the  grower  to  make  his  own  carbonate,  the  market  never  feeling  his 
demand.  With  fungicides  which  the  grower  is  unable  to  prepare  the 
conditions  are  different.  His  needs  increase  the  demand  in  the  market, 
and  increased  demand  tends  ultimately  to  lower  prices. 

The  cost  of  copper  carl)onate  when  prepared  b}-  the  grower  will 
depend  upon  the  cost  of  copper  sulphate  and  sal  soda.  Quotations  of 
March  and  April,  1899,  placed  copper  sulphate  at  5  cents  per  pound 
by  the  barrel  and  sal  soda  at  3*0  of  a  cent  per  pound  in  like  quan- 
tity. At  these  rates  the.  grower  should  be  able  to  prepare  the  car- 
bonate of  copper  at  about  12.3  cents  per  pound.  Quotations  on  larger 
lots  of  sal  soda  and  copper  sulphate  placed  the  price  at  -jV  of  a  cent 
and  41  cenfe  per  pound,  respectively.  At  these  prices  the  raw  mate- 
rials for  a  pound  of  copper  carbonate  would  cost  about  11.8  cents. 
These  facts  bhow  that  wholesale  druggists  and  manufacturing  chemists 
could  place  the  carbonate  upon  the  market  at  15  or  20  cents  per  pound 
and  still  make  a  good  profit,  even  when  Iniying  their  sodium  carbonate 
and  copper  sulphate  in  the  o^^en  market.  If  we  go  a  step  farther 
back,  howeveb",  we  may  see  that  the  first  cost  of  copper  carbonate  can 
be  greatlv  reduced  below  any  figures  here  given.  Ten-elevenths  of 
the  cost  is  seen  to  depend  upon  the  price  of  copper  sulphate,  and  the 
first  cost  of  tl^is  latter  depends  upon  the  cost  to  the  manufacturer  of 
sulphuric  acid\and  copper.  Both  of  these  articles  may  be  produced 
as  l)y -products  lof  modern  smelting  processes.  A  firm  at  Blacksburg, 
S.  C,  informs  the  writer  that  they  employ  gold-bearing  pyrites  for 
the  manufacture  of  sulphuric  acid,  the  sulphur  fumes  being  driven 


NATURE    ANT)    SOiniCE    OF    Sl'RAYTXO    MATERIALS.  185 

ori'  witli  heat  and  coiKlciiscd  in  lead  cliaiiilxTs  in  the  usual  way.  The 
acid,  the  linn  states.  i)ays  tlic  cxjicmscs,  licncc  the  uold  colU'cted  is  a 
l)y-])r()duct  witli  tlicm.  For  tlic  same  purpose  sulphur  may  )je  obtained 
by  heat  from  several  kinds  of  jiyrites — that  is,  from  the  sulphides  of 
copper  aiul  iron.  As  already  shown  in  tin*  notes  on  copper  sulphate, 
copper  for  the  pnxhiction  of  this  chemical  may  l)e  d(M-ived  largely 
from  the  mattes  of  silver  sineltino-  works.  In  view  of  the  fact  that 
both  the  cop))er  and  sulphur  of  eo})per  suli)hate  may  be  olttained  as 
))V-products  in  the  exttMisive  g'old  and  silver  smeltinji'  works,  the  tirst 
cost  of  this  cluMuii-al  can  certainly  ])e  placed  at  a  figure  admitting  of 
the  manufacture  of  copper  carbonate  at  a  very  low  cost.  It  could 
prol)ably  )»e  placed  on  the  mark(>t  to-day  by  the  leading  smelting 
companies  at  15  cents  per  pound  and  still  leave  a  liberal  profit  on 
first  cost.  It  is  to  be  hoped  that  this  matter  will  ])e  looked  into  by 
some  of  the  larger  smelting  firms,  and  that  the  carl)onate  of  copper 
may  soon  be  had  on  the  market  at  prices  which  are  not  prohibitive  to 
its  purchase  by  the  horticulturists  of  the  country.' 

AMMONIA  {forrmda  NH  3). 

1  Ammonia  is  of  gaseous  nature  and  strongly  alkaline  in  reaction. 
It  is  readily  taken  up  or  dissolved  in  water,  in  which  form  it  is  used  in 
preparing  the  ammoniacal  copper  carl)onate,  eau  celeste,  and  modified 
eau  celeste — three  of  the  more  important  copper  spraj's.  A  strong 
solution  of  ammonia  may  ))e  commonly  had  on  the  market  or  from  the 
mamifacturers.  Such  a  solution  contains,  by  weight,  about  28  per 
cent  of  ammonia  gas,  and  is  sold  as  26°  ammonia,  as  shown  by  Baume's 
hydrometer  test.  A  weaker  solution  is  often  prepared  by  druggists 
and  is  sold  as  anmionia  Avater,  or  aqua  ammonia.  This  often  contains 
no  more  than  10  per  cent  of  ammonia  gas,  and  is  obtained  by  reducing 
the  stronger  article  wnth  water.  It  is  scarcely  necessary  to  add  that 
there  is  no  economy  in  buying  this  dilute  liquid.  The  price  is  apt  to 
be  out  of  proportion  to  the  strength,  and  if  quantities  are  to  be  shipped 
long  distances  there  is  a  needless  increase  of  freight,  owing  to  the 

'The  following  quotations  on  copper  carljonate  were  received  March,  1899:  St. 
Ijfiuis  quoten  lO-pound  lots  at  272  cents  per  pound,  100-pound  lots  at  2-5  cents  per 
pound,  and  1,000-pound  lots  at  2,3  cents  per  pound,  f.  o.  b. ;  one  Philadelphia  tinn 
quotes  10-pound  lots  at  2.3  cents  per  pound,  100-pound  lots  at  22  cents  per  pound, 
1,000-pound  lots  at  21  cents  per  pound,  f.  o.  b.,  and  a  second  house  quotes  28  cents  per 
pound  for  ordinary  quantities  and  21  cents  per  pound  by  the  barrel;  New  York 
quotes  10-pound  lots  at  .3-5  cents  per  pound,  100-pound  lots  at  28  cents  per  pound,  and 
1,000-pound  lots  at  22  cents  per  pf)und  f.  o.  b. ;  Boston  quotes  10-j)oiuid  lots  at  20  cents 
per  poimd,  100-pound  lots  at  18  cents  per  pound,  and  1,000-pound  lots  at  16  cents  per 
poiuid. 

The  writer  invites  attention  to  the  great  variation  in  quotations  from  different 
centers  of  trade.  It  is  satisfactory  to  note  that  (juotations  just  received  from  Boston 
indorse  the  view  already  expressed,  that  carhonate  of  copper  can  be  placed  \\\)on  the 
market  at  about  15  cents  perpoimd  and  leave  a  sufficient  profit  10  the  manufacturer. 


186         PEACH    LEAF    CURL:    ITS    NATURE    AND    TREATMENT. 

added  percentage  of  water.  It  is  always  desirable  to  specif}^  the 
strength  of  the  ammonia  solution  when  obtaining  quotations. 

Plants  and  animals  furnish  the  main  sources  of  commercial  ammonia. 
In  each  case  the  ammonia  is  obtained  through  the  decomposition  or 
destructive  distillation  of  the  organic  matter.  Mr.  Mallinckrodt,  of 
the  Mallinckrodt  Chemical  Works,  of  St.  Louis,  and  president  of  the 
Pacific  Ammonia  and  Chemical  Company,  states  that  there  are,  as 
already  indicated,  but  two  prime  sources  from  which  aqua  ammonia  is 
obtained,  viz,  "bone  liquor,-'  obtained  as  a  by-product  in  the  manu- 
facture of  bone  coal,  and  "gas  liquor,"  obtained  from  the  scrubbing 
of  gas  in  works  for  the  manufacture  of  coal  gas.  A  similar  source  is 
also  found  in  the  making  of  coke.  It  is  further  stated  that  ammonia 
is  obtained  from  bone  liquor  almost  exclusively  in  the  form  of  sulphate 
of  ammonia,  often  of  crude  quality,  which  is  used  in  the  manufacture 
of  fertilizers.  Gas  liquor  is  partly  worked  into  a  sulphate  of  superior 
quality,  but  mostly  into  aqua  ammonia,  by  what  is  called  the  direct 
process.  It  is  redistilled  and  aqua  ammonia  made  therefrom.  Aqua 
ammonia  ol)tained  from  this  source  is  largely  used  in  the  manufacture 
of  ice  and  for  other  technical  purposes.  Obtained  in  this  wa}'^,  it  is 
said  to  be  the  cheapest  article  of  good  quality  that  can  be  supplied. 

A  crude  concentrated  ammoniacal  liquor  is  also  largely  made  by 
concentrating  gas  liquor  without  purification.  This  concentration  is 
carried  on  mainly  at  smaller  works  for  the  purpose  of  transporting  the 
liquors  in  a  more  concentrated  form,  to  save  the  expense  of  freight,  to 
works  where  crude  liquor  is  redistilled  and  manufactured  into  pure 
aqua  ammonia.  The  concentrated  liquor  is,  however,  also  largely  used 
in  the  preparation  of  nitrate  of  ammonia,  which  is  used  in  the  manu- 
facture of  powder,  but  most  largely  in  the  manufacture  of  soda  ash. 
This  crude  liquor  contains,  besides  a  small  amount  of  free  ammonia 
(NH3),  a  considerable  amount  of  carbonate,  sulphide,  cyanides,  and 
other  ammonia  salts,  together  with  tarry  and  empyreumatic  matter 
resulting  from  the  destructive  distillation  of  coal.  The  strength  of 
this  liquor  can  not  be  made  greater  than  15  to  20  per  cent,  and  it  is 
doubtful  if  it  could  be  advantageously  used  as  a  suljstitute  for  aqua 
ammonia  in  the  preparation  of  sprays.  The  ammoniacal  liquors  obtained 
in  the  manufacture  of  coal  gas  are  entirely  a  by-product. 

As  the  gas  works  of  the  United  States  have  been  largely  supplanting 
coal  gas  with  water  gas,  in  the  manufacture  of  which  ammonia  is  not 
obtained,  the  quantity  of  ammonia  produced  in  the  country  has  been 
steadily  decreasing,  and  the  demand  is  being  supplied  principally  from 
England.  Both  aqua  ammonia  and  anh3'drous  ammonia  are  made 
largely  from  imported  sulphate  of  ammonia,  and  very  large  quantities 
of  the  imported  article  are  also  consiuned  in  the  manufacture  of 
fertilizers.^ 


^San  Francisco's  quotation  on  ammonia  water  of  26°  hydrometer  test,  in  drums  of 
about  750  pounds,  f.  0.  b.,  is  7^  cents  per  pound. 


NATURE    AND    SOURCE    OF    SI'KAYINd    MATERIALS.  187 

SODIUM  CARBONATE  {formula  NajCOj-lOHgO). 

Sodium  carbonate,  sal  .soda,  or  washing  soda  is  used  in  making  car- 
bonate of  coppiM-  from  the  sul})hate  of  copper  and  in  preparing  the 
modified  eau  celeste.  As  obtained  in  the  market  it  is  in  colorless, 
monoclinic  crystals,  showing  a  strong}}^  alkali n(>  reaction  to  litmus 
j)aper.  When  exposed  to  the  air  nuicli  of  the  water  of  crystallization 
is  lost  from  the  ciystals,  Avhich  rapidly  effloresce  or  slake  to  a  white 
powder.  A^'llen  perfect,  nearly  two-thirds  of  the  crystals,  b}^  weight, 
is  water. 

Carbonate  of  soda  dissolves  in  1.(3  parts  of  water  at  59'^  F.  and  in 
0.2  part  of  boiling  water.  When  a  solution  of  sal  soda  is  added  to 
the  solution  of  copper  sulphate  in  making  copper  carl)onate,  or  to  any 
other  acid  solution,  a  decided  efl'ervescence  takes  place,  so  that  in 
making  the  copper  carbonate  the  two  solutions  used  should  be  united 
slowly  or  they  may  overflow  the  containing  A'essels.  The  more  com- 
mon impurities  found  in  sodium  carl)onate  are  sodium  chloride 
(common  salt)  and  sodium  sulphate  (Glauber's  salt).  These  impurities 
are  due  to  the  source  and  manner  of  manufacture  of  the  sal  soda,  but 
are  not  usualh'  present  in  the  latter  in  sufficient  amount  to  require 
attention  in  the  spray  work  being  considered. 

The  sources  of  sodium  carbonate  are  somewhat  luuuerous,  Imt  the 
commercial  supply  of  to-day  is  derived  mainly  from  common  salt  or 
from  natural  deposits  of  the  carbonate.  In  nearly  all  arid  countries 
carbonate  of  soda  is  frequently  found  in  the  soil  in  such  quantities  as 
to  be  injurious  to  vegetation.  W^est  of  the  Missouri  River  large  accumu- 
lations of  the  different  soluble  salts  of  the  soil  are  frequenth^  met 
with.  In  the  East  such  accumulations  are  prevented  by  the  greater 
rainfall,  the  salts  being  eventually  washed  from  the  soil  and  carried  to 
the  sea,  but  in  the  West  they  often  coat  the  ground,  appearing  white 
or  black,  and  are  known  as  '"  alkali  beds,''  owing  to  the  frequent  pres- 
ence of  strongly  alkaline  salts,  such  as  sal  soda.  The  most  abundant 
constituents  of  these  deposits  are  sodium  sulphate,  sodium  chloride, 
and  sodium  carl)onate.  The  sodium  chloride  and  sodium  carbonate  are, 
when  in  excess,  so  injurious  to  vegetation  as  to  constitute  a  leading 
bane  of  the  horticulturist  of  the  western  half  of  the  I'nited  States.  In 
the  great  plateau  region  between  the  Rocky  Mountains  and  the  Sierra 
Nevada  and  Cascade  ranges  are  vast  stretches  of  alkaline  soils,  the 
soluble  salts  of  which  accunudate  in  lakes  and  along  water  courses 
through  the  drainage  oi  the  winter  rains.  During  the  long,  dry  sum- 
mer these  waters  evaporate  to  a  considerable  extent,  leaving  the  salts 
deposited  along  the  margins  of  the  lakes  and  rivers.'  In  some  cases 
these  deposits  of  alkali  are  conq)<)sed  lai'gely  of  sodium  car])onate,  and 
in  several  instances,  after  passing  through  a  simple  purifying  process, 


'These  deposits  are  very  well  sliown  in  the  illustiatiuns  of  I'>ull.  No.  14,  Division 
of  Soils,  U.  S.  Dept.  of  Agr. 


188    PEACH  LEAF  CUKL:  ITS  NATURE  AND  TREATMENT. 

this  salt  is  obtained  in  a  quite  pure  state,  the  original  deposits  contain- 
ing- as  high  as  90  per  cent  of  sal  soda.  This  latter  is  obtained  from 
the  soda  lakes  of  South  America,  Egypt,  etc. ,  as  well  as  from  those  of 
the  United  States.  There  are  several  such  soda  lakes  in  Wyoming, 
Nevada,  and  California.  Large  amounts  of  sal  soda  are  crystallized 
from  crude  carbonate  of  soda  obtained  from  Soda  Lake,  nearRagtown, 
Nev.  This  lake  is  known  as  Big  Soda  Lake,  to  distinguish  it  from  a 
smaller  soda  lake  near  by.  The  lake  is  a  beautiful  sheet  of  water,  lying 
in  a  depression  of  the  desert,  the  water  being  about  150  feet  in  depth  at 
the  deepest  point.  It  is  very  close  to  the  old  emigrant  road  running 
from  the  sink  of  the  Humboldt  River  to  Carson  River.  The  separa- 
tion of  carbonate  of  soda  from  the  waters  of  this  lake  is  largel}'^  by 
solar  evaporation.  In  the  fall  the  salts  deposited  are  taken  up,  Avashed, 
passed  through  a  furnace,  and  shipped  in  sacks  to  San  Francisco,  where 
the  soda  is  refined  and  bleached  for  various  uses.  The  principal  uses 
on  the  Pacific  coast  are  in  glass-making  and  borax-making.  It  is 
stated  that  sal  soda  obtained  as  here  descri})ed  is  practically  a  pure 
article,  though  the  natural  color  is  somewhat  yellow  or  brownish.  It 
is  generally  useful,  except  as  a  fancy  article  for  the  retail  trade.  For 
such  purposes  it  nuist  be  bleached  with  chloride  of  lime,  after  which 
it  presents  beautiful  crj^stals. 

There  is  also  a  large  plant  in  operation  at  Owens  Lake.  Cal.,  get- 
ting out  carbonate  of  soda  from  the  waters  for  the  Pacific  market. 
This  product,  with  that  alcove  described,  is  nearl}^  equal  in  strength 
and  purity  to  the  eastern  and  the  imported  product,  so  much  so  that 
consumers  are  safe  in  using  the  western  product,  if  desired.  All  or 
most  sodas  (carbonates)  found  on  the  Pacific  coast  proper  are  in  the 
form  of  sesquicarbonates,  and  are  often  so  much  contaminated  with 
sulphates  and  chlorides  that  much  expense  is  entailed  in  their  separa- 
tion, and  they  are  therefore  of  little  value  as  sources  of  supply. 

The  second  great  commercial  source  of  sal  soda  is  common  salt. 
The  salt  deposits  of  the  country  are  vast  and  inexhaustible  in  quantity. 
The  Onondaga  Salt  Group  of  the  Upper  Silurian  alone  underlies 
much  of  the  large  extent  of  country',  as  well  as  the  Great  Lakes,  situ- 
ated between  Salina,  N.  Y.,  and  Green  Bay,  Wis.  At  certain  points 
the  salt  depqsits  of  this  group  are  known  to  exceed  100  feet  in  thick- 
ness. The  deposit  is  tapped  by  wells  at  Warsaw,  N.  Y.,  in  western 
Ontario,  in  eastern  and  in  western  Michigan,  and  elsewhere.  The  rock 
salt  of  wester^  Michigan  is  20  to  80  feet  in  thickness,  and  is  reached  at 
a  depth  of  1,800  to  2,200  feet.  Other  large  salt  deposits  are  found  in 
Kansas  and  in  numerous  other  portions  of  the  country. 

Sal  soda  is  riSianufactured  from  salt  on  a  commercial  scale  according 
to  two  leading  ^Drocesses.  The  older  of  these  is  known  as  the  Leblanc 
process,  and  hat?  been  extensively  employed  in  England  and  through- 
out Europe.     It  involves  two  steps  in  the  manufacture,  (1)  the  conver- 


NATURE    AND    SOURCE    OF    SPRAYING    MATERIALS.  189 

sion  of  salt  into  sodium  sulphate,  and  (2)  the  decomposition  of  sodium 
sulphate  and  its  conversion  into  sodium  carbonate.  The  tirst  opera- 
tion is  known  as  the  "salt-cake""  process,  and  the  second  as  the  ''soda- 
ash  "  process.  The  tirst  step  is  carried  out  by  the  application  of  sul- 
phuric acid  to  the  salt  and  the  decomposition  of  both  in  a  fui-nace,  the 
doul)h'  (U^composition  resultin»i'  in  the  formation  of  hydrocidoric  acid 
and  sodium  sulphate.  The  h3'drochloric  acid  is  condensed  and  pre- 
served, while  the  salt  is  converted  ])v  heat  into  a  hard  cake  of  acid 
sodium  sulphate.  There  is  usually  in  this  cake,  however,  more  or  less 
unaltered  sodium  chloride.  In  the  second  step  the  salt  cake  is  pul- 
verized and  mixed  with  an  e([ual  Aveio-ht  of  pulverized  limestone  or 
chalk  and  half  its  weit)lit  of  tine  coal.  This  mixture  is  heated  to 
fusion  in  a  furnace,  being  constantl}'  stirred  or  revolved.  The  com- 
bustion of  the  coal  under  the  heat  which  is  maintained  seems  to  con- 
vert the  sodium  sulphate  into  sodium  sulphide,  and  the  decomposition 
of  the  sodium  sulphide  and  limestone,  with  the  interchange  of  ele- 
ments, produces  calcium  sulphide  and  sodium  carbonate.  The  resulting 
mass  is  cooled  in  iron  receivers,  broken  up  tinely,  and  digested  in  tepid 
water.  The  alkali  dissolves  and  leaves  the  insoluble  impurities.  The 
sodium  solution  is  evaporated,  and  when  dry  the  mass  is  calcined  with 
one-fourth  its  weight  of  sawdust,  to  more  fully  convert  the  alkali  into 
carbonate.  This  product— the  soda  ash  of  commerce — is  again  dis- 
solved in  hot  water,  and  the  solution  filtered  and  allowed  to  cool.  As 
the  solution  cools  the  carbonate  of  soda  is  deposited  in  large,  trans- 
parent crystals,  such  as  are  supplied  to  the  trade.  Soda  ash  was 
formerly  largely  imported  from  England,  but  in  the  last  few  years  has 
been  made  in  the  I'^nited  States  to  a  very  large  extent.  The  dissolv- 
ing of  the  soda  ash  and  the  crystallizing  of  the  sal  soda  is  carried  on 
extensively  by  tirms  not  manufacturers  of  the  ash.  A  St.  Louis  firm 
states  that  they  crystallize  the  solution  of  soda  ash  in  tanks  holding  about 
8,000  pounds  each.  After  the  crystallization  has  progressed  sufficiently, 
which  takes  from  ten  to  fourteen  days,  according  to  the  temperature  of 
the  weather,  the  mother  lye,  which  contains  all  the  impurities,  is 
drawn  off  and  the  sal  soda  is  then  broken,  dried,  and  packed  in  barrels. 
It  is  stated  that  a  newer  process  is  to  crystallize  the  solution  in  small 
tanks,  holding  perhaps  200  pounds.  In  this  small  (piantily  the  liquid 
crystallizes  in  a  very  short  time,  say  over  night,  but  does  not  give  any 
mother  lye,  and  consequently  no  impurities  are  removed. 

A  system  entirely  diti'erent  from  the  Leblanc  process  is  in  use  in  the 
United  States  in  some  of  the  leading  salt  regions  and  has  come  very 
largely  into  use  in  Europe.  It  is  known  as  the  ammonia  soda  process, 
or  the.  Solvay  process.  It  consists  in  decomposing  a  solution  of  com- 
mon salt  with  ammonium  bicarbonate,  whereby  the  greater  part  of 
the  sodium  is  precipitated  as  bicarbonate,  while  the  ammonia  remains 
in  solution  as  auunonium  chloride.     This  latter  salt  is  heated  with 


190    PEACH  LEAF  CURL:  ITS  KATURE  AND  TREATMENT. 

lime  to  liberate  ammonia,  which  is  then  reconverted  into  bicarbonate 
by  the  carbonic  acid  evolved  in  the  conversion  of  the  sodium  bicar- 
bonate into  monocarbonate  by  heat.  The  ammonium  bicarbonate  thus 
reproduced  is  employed  to  decompose  fresh  portions  of  sodium  chlo- 
ride, so  that  the  process  is  made  continuous.^ 

SULPHUR  {symbol  S). 

The  value  of  sulphur  as  a  fungicide,  insecticide,  and  germicide  nas 
been  known  for  many  years.  Its  use  in  a  powdered  state  has  been 
long  followed  in  hothouses  and  vineyards,  and  its  application  in  the 
treatment  of  parasitic  skin  diseases  of  man  and  the  lower  animals,  and 
in  the  control  of  fermentation  in  fruits  and  wines  is  equally  well 
known.  In  connection  with  potash  and  soda  it  has  been  applied  to 
the  treatment  of  fungous  diseases  in  the  form  of  sulphides  of  these 
bases. 

The  recent  marked  use  of  sulphur  in  preparing  sulphide  of  lime  for 
the  spraying  of  trees  is  believed  to  have  been  lirst  suggested  in  Cali- 
fornia, the  idea  coming,  it  is  thought,  from  the  use  of  sulphur  in  a 
similar  form  as  a  dip  to  Idll  scab  mites  on  sheep.  The  spraying  of 
trees  infested  by  scale  insects  was  a  natural  application  of  its  known 
insecticidal  qualities  to  the  needs  of  the  orchard.  In  combination  with 
lime  and  salt  it  is  now  very  widely  used  on  the  Pacific  coast.  These 
chemicals  are  boiled  together  for  a  considerable  time,  and  result  in  the 
formation  of  one  or  more  of  the  sulphides  of  calcium  in  liquid  form. 
While  the  value  of  this  spray  is  well  established  in  regions  west  of  the 
Rocky  Mountains,  its  introduction  in  the  East  has  been  slow,  though 
it  is  almost  certain  to  have  a  wide  application  in  that  section  in  coming 
years,  when  the  full  importance  of  winter  spraying  for  the  control  of 
insect  pests  and  fungous  diseases  is  more  fully  appreciated.  This  is 
more  especially  true  where  both  of  these  classes  of  diseases  occur  at 
one  time  on  the  same  host  plant. 

Sulphur  is  obtainable  in  the  market  in  several  forms  and  degrees  of 
purity.  The  forms  most  common  are  known  as  brimstone,  the  flour 
of  sulphur,  and  flowers  of  sulphur.  Brimstone  is  sulphur  in  the  solid 
form,  flour  of  sulphur  is  ground  brimstone,  and  flowers  of  sulphur  is 
sulphur  which  has  been  sublimed.  Common  brimstone  is  the  cheapest 
form  on  the  market,  flour  of  sulphur  stands  next  in  price,  while 
flowers  of  sulphur  comes  still  higher.     The  purity  of  any  of  these 

^Quotations  on  sal  soda  were  received  as  follows  during  March  and  April,  1899: 
San  Francisco  qiuotes  50-sack  lots  at  60  cents  per  100  poimds,  10-barrel  lots  at 
70  cents  per  100  pounds,  and  smaller  quantities  at  75  cents  per  100  pounds;  Los 
Angeles  quotes  %y  the  barrel  $1.25  per- 100  pounds,  and  by  the  car  in  sacks  $1  per 
100  pounds;  St.  l^ouis  quotes  by  the  car  load  in  barrels  55  cents  per  100  pounds; 
New  York  quotes\  f.  o.  b.  Syracuse,  in  jobbing  lots,  barrels  of  375  pounds,  40  cents 
per  100  pounds;  ^'^^irport,  N.  Y.,  quotes  50  cents  per  100  pounds,  f.  o.  b. 


NATURE    AND    SOURCE    OF    SPRAYINO    MATERIALS.  191 

forms  is  usually  sutiiciently  hioh  for  the  use  of  tho  horticulturist. 
Brimstone  and  flour  of  sulphur  are  usually  about  98  per  cent  pure, 
while  flowers  of  sulphur  is  almost  entirely  pure.  Brimstone  weighs 
most,  flour  of  sulphur  less,  and  flowers  of  sulphur  least  for  a  like 
bulk. 

The  horticulturist  uses  sulphur  in  all  the  above-named  forms,  brim- 
stone being-  empkwed  for  bleaching  fruit,  nuts,  etc.,  while  flour  and 
flowers  of  sulphur  are  used  in  field  work  for  the  control  of  insect  and 
fungous  pests.  A  simple  mode  by  which  one  may  test  the  purity  of 
sulphur  is  to  weigh  out  any  desired  amoiuit  and  then  drj'^  and  burn 
it;  the  weight  of  the  remaining  incombustible  portion,  added  to  the 
amount  of  weight  lost  in  drying,  determines  the  amount  of  impurities. 

The  sources  of  the  sulphur  supply  of  the  United  States  are  numer- 
ous and  varied.  A  large  amount  of  crude  sulphur  is  imported, 
although  much  of  the  sulphur  now  used  in  the  production  of  copper 
sulphate,  sulphuric  acid,  and  various  other  chemicals  is  obtained  in 
the  United  States  through  the  decomposition  of  several  native  metallic 
sulphides,  such  as  the  sulphides  of  iron  and  copper,  which  are  known 
as  iron  and  copper  pyrites.  It  has  been  estimated  that  the  amount  of 
sulphur  consumed  in  the  United  States  in  1892  was  218,154  tons.  The 
sources  of  this  sulphur  were  as  follows: 

From  100,721  tons  of  imported  brimstone  (98  per  cent) 98,707  tons. 

From  1,825  tons  of  domestic  brimstone  (98  per  cent) 1,787  tons. 

From  210,000  tons  of  imported  pyrites  (43  per  cent) 90,300  tons. 

From  119,000  tons  of  domestic  pyrites  (44  per  cent) 52,360  tons. 

At  the  present  time  the  amount  used  is  probably  nuich  greater  than  in 
18:i2. 

Great  deposits  of  native  sulphur  are  found  in  many  foreign  coun- 
tries and  in  various  portions  of  the  United  States.  Most  of  the 
natural  deposits  occur  in  past  or  present  mountain  regions,  and  are 
of  volcanic  origin.  '"The  exhalations  of  volcanoes  include,  as  a  rule, 
sulphurous  acid  (SO.,)  and  sulphureted  hydrogen  (HjS),  which  two 
gases,  if  moist,  readily  decompose  each  other  into  water  and  sulphur, 
a  circumstance  which  accounts  for  the  constant  occurrence  of  sulphur 
in  all  volcanic  districts.''  It  is  estimated  that  5,000,000  tons  of  sulphur 
exist  in  one  deposit  in  Japan.  The  deposits  of  Sicily  are  famed  the 
world  over,  and  100  distinct  workings  are  said  to  exist  in  that  island. 
In  central  Sicily,  at  Assoro,  Imera,  Villarosa,  and  elsewhere,  large 
amounts  of  brimstone,  in  the  form  of  short  truncated  pyramids,  are 
commonl}^  seen  piled  near  the  railroad  stations,  as  wood  is  piled  in  the 
United  States.  These  large  blocks,  probably  weighing  1<  lO  pounds  each, 
are  brought  to  the  railroad  on  the  backs  of  donkeys  dri\'en  down  from 
the  mines  in  the  mountains  in  long  trains.  Large  refineries,  devoted 
to  the  refining  of  such  l)rimstone,  are  located  at  Catania.  The  annual 
outputof  sulphur  in  Sicily  is  said  to  exceed  300,000  tons,  and  the  present 


192    PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT, 

importation  of  the  United  States  from  Sicily  is  about  120,000  tons. 
The  richer  sulphur  ores  of  Sicily  run  from  30  to  40  per  cent  of  sul- 
phur.    A  considerable  quantity  is  also  imported  from  Japan. 

The  leading  native  sulphur  deposits  of  the  United  States  are  located 
in  Nevada,  Utah,  California,  \\^yoming,  and  Louisiana.  While  the 
amount  of  sulphur  ore  in  the  country  is  inexhaustible,  the  writer  is 
informed  by  a  New  York  dealer  that  not  to  exceed  3,000  tons  are 
mined  here  annually,  which,  of  course,  does  not  include  the  amount 
extracted  from  pyrites.  Respecting  the  Utah  sulphur  mines,  which 
are  located  in  the  foothills  of  the  Wasatch  Mountains  and  in  Beaver 
Count}^  al>out  200  miles  from  Salt  Lake  City,  the  writer  has  received 
the  following  interesting  data  from  Mr.  C.  F.  G.  Meyer,  of  St.  Louis: 
The  sulphur  supply  at  these  Utah  mines  is  practically  unlimited,  and 
the  price  of  the  product  is  governed  entirely  l)y  foreign  markets. 
The  sulphur  is  found  in  an  immense  bed,  the  ore  beginning  at  the  sur- 
face of  the  earth  and  extending  down  to  unknown  depths.  This  ore  is 
of  a  very  soft  character,  containing  sand,  gypsum,  and  gravel,  and 
has  from  15  to  95  per  cent  sulphur.  The  profitable  ore  is  mined 
through  open  cuts  and  hauled  on  a  tramway  to  smelters.  The  smelters 
are  cast-iron  retorts  and  hold  a  ton  of  ore.  Each  charge  is  her- 
metically sealed  and  the  retort  is  subjected  to  40  atmospheres  of  steam 
pressure.  Under  this  heat  the  sulphur  percolates,  in  the  shape  of 
liquid  sulphur,  through  the  foreign  matter  into  a  pot  below,  from  which 
it  is  drawn  off  and  passes  into  a  distilling  vat  for  the  purpose  of  per- 
mitting all  foreign  substance  to  settle  to  the  bottom  of  the  tank;  thence 
it  is  drawn  off'  into  wooden  molds,  holding  about  200  pounds,  and 
allowed  to  cool,  after  which  it  is  passed  through  a  grinding  process 
in  an  attrition  mill.  The  product  obtained  by  the  above  process  is  about 
99  per  cent  pure,  and  forms  the  flour  of  sulphur,  which  is  extensively 
used,  as  already  indicated.  For  obtaining  what  is  commonly  known 
as  flowers  of  sulphur,  which  is  chemically  pure,  the  ground  sulphur  is 
passed  through  a  resubliming  vapor  process. 

Respecting  any  possible  advantage  to  the  horticulturist  by  purchas- 
ing sulphur  reflned  in  Europe  in  preference  to  that  refined  in  the 
United  States,  a  prominent  sulphur  refiner  of  San  Francisco  has  kindly 
supplied  the  following  facts: 

The  sulphur  refined  is  mostly  from  imported  Sicilian  and  Japanese 
products.  While  there  exists  the  remnant  of  a  former  prejudice 
against  California  sulphur,  it  should  be  of  interest  and  value  to  know 
that  there  is  absolutely  no  difference  between  that  manufactured  here 
and  that  manufactured  in  France,  Italy,  Denmark,  and  other  European 
countries.  Both  start  with  the  same  raw  material  coming  from  Sicily, 
the  same  apparatus  is  employed,  and  even  experienced  foreigners  are 
hired  to  refine  the  brimstone  in  the  identical  manner  in  which  it  is 
treated  in  the  \ above  places.     There  comes  to  the  horticulturist  no 


NATURE    AND    SUUKCE    OF    SPRAYING    MATERIALS.  193 

advantaofc,  therefore,  to  offset  tlic  present  duty  of  $8  per  ton  levied  on 
the  refined  imported  sulphur,  and  our  agricultural  population,  it  is 
claimed,  is  duped  when  demaiidino-  French,  Italian,  or  other  European 
refined  sulphur.  The  same  manufacturer  further  states  that  Sicily 
sulphur  of  98  per  cent  purity  is  at  present  admitted,  to  the  United 
Stat(>s  duty  free,  and  that  it  can  be  ground  or  sul)limed  in  this  country 
and  sold  at  a  price  below  the  cost  of  the  imported  foreign-refined  sul- 
phur. It  is  also  said,  as  to  the  comparative  value  to  the  horticulturist 
of  ground  (floui-)  and  of  sul)iinied  sulphur  (fiowers),  that  for  ordinary 
purposes  domestic  ground  or  powdered  sulphur,  which  averages  less 
than  1  per  cent  of  impurities,  will  answer  all  requirements  in  a  wash, 
being  finer  tlian  the  imported,  the  onh'  impurity  being  a  neutral, 
inert  volctmic  ash.  The  sublimed  sulphur,  as  before  stated,  is  identical 
with  the  imported  and  contains  little,  if  any,  trace  of  anything  but 
elementary  sulphur.  It  is  lighter  in  bulk  and  more  stringy  than 
ground  sulphur  (if  examined  under  the  microscope),  but  is  not  usually 
enough  better  for  agricultural  purposes  to  offset  the  difference  in 
price.  In  other  words,  the  difference  in  purity  percentage  between 
ground  sulphur  and  sublimed  sulphur  is  not  in  anj^  way  commensu- 
rate with  the  difference  in  price,  and  a  great  saving  could  be  effected 
l)y  substituting  the  former  for  the  latter  in  ninety-nine  cases  out  of  a 
hundred. 

To  these  views  the  writer  would  add  that  the  flour  of  sulphur  is  cer- 
tainly what  should  be  used  in  the  preparation  of  sprays.  As  to  the  rela- 
tive value  of  flour  of  sulphur  and  flowers  of  sulphur  for  powdering  vines 
for  mildew,  there  is  a  difference  of  opinion  among  vine  growers,  the 
ease  with  which  the  fumes  are  given  ofl'  being  considered  of  prime 
importance  in  the  treatment  of  this  disease.^ 

^  Quotations  on  sulphur  in  March,  1899,  were  as  follows:  New  York  quotes  flour 
of  sulphur  in  250  pound  barrel  lots  at  $2.20  per  100  pounds,  100  pound  sacks  at  $2.15 
per  100  pounds,  and  car  loads  in  barrels  at  $1.80  per  100  pounds,  and  in  sacks  at  $1.75 
per  100  pounds,  all  f.  o.  b.  A  sec-ond  New  York  firm  quotes  roll  brimstone  at  $2  per  100 
pounds;  flour  of  suljihur,  heavy,  at  $2.20,  and  light  at  $2.25  per  100  i)ounds  by  the 
Ijarrel;  sublimed  flowers  of  sulphur  at  $2.37^  per  100  pounds,  in  carload  lots,  f.  o.  b. ; 
roll  brimstone,  $1.70  per  100  pounds;  flour  of  sulphur,  heavy,  100  pound  l)ags,  $1.75; 
250  pound  barrels,  $1.80  i)er  100  pounds;  light,  175  pound  barrels,  $1.85  per  100 
pounds;  flowers  of  sulphur,  sublimed,  $2  j)er  100  pounds.  San  Francisco  quote.s 
powdered  sulphur,  sacks  or  barrels,  by  the  car  load  at  $1.50  per  100  jjounds,  less 
quantity  at  $1.60  per  100  pounds;  sublimed  (flowers  of  sulphur),  sacks  or  barrels, 
car  load  lots,  $1.75  per  100  pounds,  less  quantity,  $1.85  per  100  pounds;  roll,  barrels 
only,  $1.85  per  100  pounds;  refined,  l)arrels  only  (quality  same  as  roll),  $1.75  per  100 
pounds;  crude,  sacks,  $1.40  per  100  pomids. 
19093— No.  20 13 


CHAPTER  XI. 

PEACH  VARIETIES  AND  NURSERY  STOCK  IN  RELATION  TO  CURL. 
COMPARISON    OF   PEACH   VARIETIES. 

It  is  a  well-known  fact  that  certain  peach  varieties  are  less  suscep 
tible  to  curl  than  others.  When  planting,  many  growers  strive  to 
select  varieties  which  are  known  to  be  comparatively  resistant.  This 
has  led  nurserj-men  to  select  and  grow  as  hardy  varieties  as  possible, 
and  such  selection  has  resulted  in  cultivated  varieties  becoming  to 
some  extent  more  hardy  than  the  majority  of  seedlings.  Of  97  peach 
growers  who  have  stated  whether,  in  their  opinion,  seedling  or  budded 
trees  are  most  affected  by  curl,  60  say  that  seedlings  are  most  affected, 
19  think  budded  trees  are  affected  most,  and  28  growers  have  observed 
no  difference  between  budded  and  seedling  trees  in  this  respect. 

In  spite  of  the  fact  that  some  varieties  of  budded  peaches  are  quite 
hardy,  many  of  the  finest  peaches  grown  are  much  subject  to  curl. 
There  are  also  varieties  which  are  hardy  in  one  locality  and  become 
very  subject  to  the  disease  when  grown  under  different  conditions. 
There  are,  in  fact,  so  many  influences,  such  as  season,  soil,  situation, 
etc.,  that  it  has  been  difficult  to  decide,  except  in  a  few  cases,  whether 
a  variety  ma}^  be  fairly  classed  as  hardy  or  susceptible.  It  is  found 
by  wide  inquiry  that  a  peach  which  is  considered  hardy  in  one  portion 
of  the  country  is  not  resistant  to  curl  in  another.  The  views  of  peach 
growers  vary  so  widely  respecting  the  hardiness  of  varieties  that  it  has 
been  thought  best  to  give  the  results  as  obtained,  rather  than  strive  to 
draw  from  them  an}^  final  conclusions.  Of  a  large  number  of  growers 
who  have  been  asked  whether  earlj'^  or  late-blooming  varieties  are 
most  affected,  70  have  expressed  their  views.  A  majority,  or  42  of 
these  growers,  think  there  is  no  difference  between  early  and  late 
blooming  varieties,  23  believe  early  blooming  varieties  most  subject 
to  the  disease,  and  only  5  believe  the  late  bloomers  most  affected.  It 
would  seem  that  the  late  blooming  varieties  maj^  be  less  liable  to 
injury,  owing  to  the  increased  warmth  when  the}'  push  in  the  spring, 
Initthe  difference  is  certainly  not  well  marked.  Respecting  the  hardi- 
ness of  early  or  late  maturing  varieties,  there  appears  to  be  little  dif- 
ference from  the  replies  to  the  circular  letter.  Among  79  peach 
growers  who  have  expressed  their  views,  22  think  early  varieties  most 
subject  to  the  disease,  16  believe  the  late  varieties  most  subject  to  it, 
and  41  think  there  is  no  difference, 
194 


PEACH    VARIETIES    IN    KELATION    TO    CURL. 


195 


Besides  the  facts  respecting  the  hardiness  of  varieties  gathered  by  a 
circular  letter  addressed  to  the  peach  growers  of  the  country  in  1893, 
the  following  list  contains  such  information  on  this  subject  as  it  has 
been  possible  to  glean  from  the  publications  accessible  to  the  writer. 
In  this  list  arc  tal)ulatod  101  peach  varieties  and  a  few  nectarines  in 
relation  to  their  resistance  to  curl.  So  far  as  possible  the  form  of  the 
glands,  the  season  of  ripening,  and  the  adhesion  of  pit  is  shown.  ^  The 
susceptibility  to  curl  is  shown  in  three  columns — little  susceptible, 
mediiun  susceptible,  and  very  susceptible.  Every  record  for  or  against 
a  variety  has  been  obtained  from  a  distinct  source  from  all  other 
records  for  that  variety,  and  the  list  includes  over  1,000  records.  As 
a  record  luidcr  medium  susceptible  or  very  susceptible  is  against  the 
variety,  showing  that  it  is  subject  to  the  disease,  these  two  columns 
are  added  and  the  siun  carried  to  a  final  column.  This  final  column 
may  thus  be  fairly  contrasted  with  the  iirst  column,  which  gives  the 
records  of  varieties  little  susceptible  to  curl.  The  entire  list  goes  far 
to  show  that  few  varieties  are  practically  free  from  curl  in  all  locali- 
ties, and  that  some  of  the  finest  varieties  are  A^ery  susceptible  to  it. 
(See  for  example  the  records  under  Crawfords  Late,  Crawf ords  Early, 
Elberta,  Heath  Cling,  Lovell,  etc.) 

Table  43. — lielatlons  of  2>each  varieties  to  peach  leaf  curl,  with  records  of  glands,  time  of 
ripenirifj,  and  adhesion  of  pit. 


No. 


Peach  varieties. 


Aigle  de  mer,  Sea  Eagle. 

Albright 

Alexander 

Alpha. 


Amelia 

Amsden 

Austin 

Beatrice 

Beers  (smock)  

Bilyeaus  Late 

Bishops  Early 

Bonanza 

Boston 

Brandvwino 

Brett  (Mrs.) 

Brices  Early 

Briggs  May 

Bronson  (seedling)  

California  (cling) 

Canada  

Cape  Clingstone 

Cape  Freestone 

Cape  Pavie. 

Chairs  (choice)  r 


'4' 


^In  some  instances  it  is  known  that  the  form  of  the  glands  of  a  variety  is  reported 
differently  by  different  writers,  and  on  this  accomit  a  few  errors  may  have  crept  into 
the  table  here  given,  but  where  it  has  been  possible  to  determine  such  questions  by 
referring  to  several  authors  it  has  bet^i  done.  Unfortunately  the  writer  has  not  l)een 
able  to  study  this  matter  in  the  orcliard  except  for  a  portion  of  the  varieties  given. 


196         PEACH    LEAF    CURL:    ITS    NATURE    AND    TREATMENT. 

Taulk  43. — Ik'lalians  of  peach  varieties  to  peach  leaf  curl,  7i-ith  records  of  gJandx,thm  of 
ripening,  and  adhesion  of  pit — Continued. 


Peach  varieties. 


5  =S  O 


Charlotte 

Chinese  (cling) 

Clemence 

Columbia 

Com  et 

Cooledge  (favorite) 

Cots  (cling) 

Cranes  Early  Yellow 

Crawfords  Early 

Crawfords  Late 

Crimson  Beauty 

Crocketts  \Yhite 

Crosby 

Doctor  Hogg 

DowTiing 

Dumont 

Early  Albert 

Early  June 

Early  May 

Early  (red)  Rareripe 

Early  Rivers 

Early  Rose - 

Early  Slocumb 

Elberta 

Ellison 

Florin 

Fords  Late  White 

Foster 

Fox  (seedling) 

General  Bid  well 

George  the  Fourth 

Georges  Late 

Globe 

Gold  Dust 

Golden  Cling 

Golden  Drop 

Governor  Briggs 

Governor  Garland 

Governor  Wood 

Grave  Cling 

Grosse  Mignonne 

Grover  Cleveland 

Hales  Early 

Hales  Late 

Hardy  White  Tuscany 

Hardy  Yellow  Tuscany 

Heath  Cling 

Heath  Free 

Henrietta,  Levys  Late 

Hills  Chile 

Honest  Abe 

Honey  Cling 

Hood  Cling 

Imperial  (early) 

Indian  Blood  (cling) 

Ingles  (seedling) 

Ironclad 

Jacques  Rareripe |     r 

Japan  Blood 

Jenny  Worrell 

Jenny  Worthen 

Jones  (seedling) 

Kalamazoo 

Kennedy  ( cling) 

Keyport  White 

Kites  Honey 

Lady  Palmerston 

La  Fleur 

La  Grange 

Large  Early  York,  Honest  John .-. . 

Large  White  Cling 

Large  Yellow 

Late  Admirable 

Late  Barnard 

Late  October 


PEACH    VARIETIES    IN    RELATION    TO    CURL. 


197 


Table  43. — Relations  of  peach  varieties  to  peach  leaf  curl,  with  records  of  glands,  time  of 
ripening,  and  adhesion  of  pit — Continued. 


N'o. 

Peaoh  varieties. 

o 

4)  „• 

O 

is 

s 

■1) 

1' 

6 

1 

3 

m 

3 
«    . 

p. 

O 

3  O 

>, 

> 

3  Lo    . 

^  (3  Q? 
0  *  « 

U)0 

r 
r 
r 

1 
1 
1 
e 

f 

c 

f 
f 

1 
1 

1 

1(11 

5 
1 
2 

2 

3 

102 

lOi 

Lewis  Scodling 

...... 

1 

'""i 

1 

13 

2 

...... 

1 

104 

1 

105 

Lola  (Miss) 

Lord  Falmerston 

r 
g 

S 

V 

e 
1 
1 
1 

f 
f 

f 
f 

1 

lOli 

1 
1 

1 
2 

2 

107 

Lovell 

15 

108 

Lovetts  White                                                   

2 

109 

1 

1 

nn 

1 

c 

I 

111 

4 

1 

2 

112 

McClish.                                               

1 

113 

McCollister 

1 

114 

e 
c 
c 

1 
1 

1 
1 

1 

115 

McDevitts  (oling)                                           

1 

1 

2 

2 

IIG 

3 

117 

1 

ns 

Moore 

r 

e 

e 
1 

e 
1 
e 

f 
f 
c 

f 
f 
f 

c 

f 

c 

f 
f 

c 

'""i' 

1 

10 
9 
4 
3 

6 

1 
2 

7 
2 

-     1 

1 

119 

Morris  AVhite 

7 

120 

T'1 

Mountain  Rose 

g 
r 

5 
11 

4 
4 

9 

122 

15 

TM 

125 

yoblesse .          

s 
S 

r 
r(V) 

e 
1 
1 

e 

1 

1 

3 

4 



'"'i' 

10 

1 

1 

120 

4 

T'7 

14 

T'8 

Onderdonk 

2 

T>c) 

Orange  Cling 

2 

ISO 

1S1 

Pallas .                

r 

e 

0 

f 
f 

1 

2 

2 
1 

1 

IS'' 

2 

13S 

Perkins 

1 
3 

1 

134 

F'icquets  Late 

r     1     1 

i 

3 

5 

1S5 

1 

ISfi 

Prtitt 

r 
g 

e 

1 

f 
f 

1 

1 

1S7 

President 

1SH 

Red  Ceylon 

1 
1 

1 

139 

Red  Cheek 

g 

1 

f 

i 
1 

1 

140 

141 

Reeds  Crawford 

g 

e 

f 

1 
1 

1 

142 

Reeds  Early  Golden. .                                     .        

1 

143 

Reeves  Favorite 

g 

1 

f 

i 

4 

4 

144 

145 

Reine  de  vergers,  Orchard  Queen           

r 
r 
g 
s 

g 

s 
r 

1 
c 
1 
e 

1 
e 

1 

f 

f 
c 
f 
c 

f 
f 

1 

1 

146 

Richmond 

1 

147 

1 

...... 

1 
1 

13 
1 

1 

148 

Roval  George 

1 

149 

Rlinvons  Orange 

3 

150 

Sallie  Worrell 

1 

151 

Sal  way 

11 

12 

25 

15' 

1 

153 

Sellers  Cling .  .           

c 

f 

f 

5 

1 
1 

1 

1 
1 

1 

154 

Sellers  Free 

3 

155 

Sener 

r 

e 

156 

Shinns  Rareripe ..             

157 

g 

1 

f 

1 

2 

1.58 

Silver  Twig .        . 

1 

159 

Smocks  Free,  HI.  George 

r 

r 
r 
r 

g 
r 
r 

1 
1 
1 

u 
e 
1 

1 
1 

f 

f 
f 
f 
f 
f 
f 
f 

c 

f 

f 
c 

f 

7 
3 

5 

1 

,8 

1 

100 

11 

161 

Snow  . .  1 

162 

4 
4 

2 

4 

163 

St.  John 

7 

164 

Steadly 

2 

165 

■■■■j- 
...... 

106 

1 
2 

10 

1 

6 

1 

167 

Strawberry  Cling 

4 

168 

g 
g 
g 
r 

1 

0 

1 
1 

16 

169 

1 

170 

171 

6 
1 

1 

6 

172 

5 

4 

5 

17S 

g 
g 

1 
e 

f 
f 

1 

174 

Tillotsou  (early ) 

3 

2 

2 

198 


PEACH  LEAF  CURL:  ITS  NATURE  AND  TREATMENT. 


Table  4o. — ReUdions  of  peach  varieties  to  peach  leaf  curl,  with  records  of  glands,  time  of 
ripening,  and  adhesion  ofjjit — Continued. 


Peach  varieties. 


3  <a 


175 
176 
177 
178 
179 
180 
181 
182 
183 
184 
185 
186 
187 
188 
189 
190 
191 


192 
193 
194 
195 
196 
197 


Thissells  White 

Troths  (early) 

Tuskena,  Tuscan  Clini/. 

Ulatis 

Wager 

Wards  Late  Free 

Waterloo 

Wheatland  (earlv) . . . . . 

White  English 

White  Melocoton 

Wilcox  Cling 

Wiley 

Wilkins  Cling 

Willow  (peach) 

Winters 

Wonderful 

Yellow  Rareripe 


NECTARINES. 


Boston 

Early  Newington 

Hardwicks  Seedling . 

Lord  Napier 

Rivers  Orange 

Victoria 


A  digest  of  98  reports  on  peach  varieties  in  respect  to  the  form  of 
glands,  earliuess  or  lateness  of  ripening*,  and  adhesion  or  nonadhesion 
of  the  pits,  as  these  characters  may  or  ma}^  not  be  related  to  suscepti- 
bility to  curl,  is  given  in  the  following-  table. 

Table  44. — Comparative  susceptibility  of  98  peach  varieties  in  relation  to  form  of  glands, 
earliness  or  lateness  of  rijiening,  and  adhesion  or  nonadhesion  of  pit. 


Character  of  glands. 


Period  of  ripening 
and  adhesion  of 
pit. 


Number  of  varie- 
ties— 


Very 
suscepti- 
ble. 


Little 
suscepti- 
ble. 


Total  varieties — 


Very 
suscepti- 
ble. 


Little 
suscepti- 
ble. 


Reniform,  50  varieties. 


Globose,  42  varieties. 


Serrate,  6  varieties. 


Early. 
Late.. 
Free.. 
Cling . 
Early. 
Late . . 
Free.. 
Cling . 
Early. 
Late.. 
Free.. 
Cling . 


21 


In  the  above  table  a  most  striking  correlation  appears  between 
peach  varieties  with  serrate  leaves  and  susceptibility  to  curl.  All 
the  six  varieties  for  w'hich  full  information,  could  be  obtained  are 
little  susceptible,  which  is  all  the  more  interesting  from  the  fact  that 
the  varieties  with  serrate  leaves  have  long  been  known  to  be  veiy 


PEACH    VARIETIES    IN    RELATION    To    CTRL. 


199 


subject  to  mildew.  A  list  of  seven  such  \  :irictics  for  which  tlic  char- 
acters of  the  leaves  have  been  obtaina))lc  is  ht're  given  in  contrast  to 
the  above. 

Table  45. — List  of  jicaclie^  s-ahjcd  Id  niildcir. 


Name. 

Cliiiracteristios. 

Gland.s  or  leaves. 

Ripens. 

Adhesion. 

Serrate  

Early 

...do 

Free. 

do 

Do. 

do 

...do 

I'aiiv  York                                     

do 

...do 

Free. 

do 

...do 

Do. 

do 

...do 

Do. 

Tillotson      . .            .              

do 

...do 

Do. 

Some  correlations  of  the  shape  and  absence  of  leaf  glands  with  the 
time  of  maturity  of  the  fruit  and  the  adhesiveness  of  the  pit  have 
been  compiled  from  over  400  varieties,  and  these  correlations  are 
shown  in  the  table  Avhich  follows. 

T.\BLE  46. — Correlation  of  shape  or  absence  of  the  leaf  glands  of  the  peach  with  the  period 
of  maturity  of  the  fruit  and  the  adhesiveness  or  iionadhesiveness  of  the  pit. 


Reniform 
glands. 

Globose 
glands. 

Serrate 

leave.s,  or 

without 

glands. 

Earl  V 

4f) 
140 
124 
C2 
35 
89 
14 
48 

130 
50 

166 
14 

120 

46 

10 

4 

32 

Late 

4 

Free                                         

32 

Cling 

4 

28 

3 

4 

1 

This  table  shows  that  of  208  early-fruiting  varieties,  46  have  reniform 
glands,  VM)  globose  glands,  and  32  serrate  leaves;  while  of  194  late 
varieties,  140  have  reniform  glands,  50  globose  glands,  and  4  serrate 
leaves.  In  other  words,  of  the  early  varieties  given  there  are  nearly 
three  times  as  many  with  globt)se  glands  as  with  reniform  glands. 
On  the  other  hand,  of  the  late  \arieties,  there  are  nearly  three  times 
as  many  with  reniform  glands  as  with  globose  glands.  The  table 
also  shows  that  there  arc  120  early  free  globose  to  35  early  free  reni- 
form \  aril  tics,  wdiile  there  are  89  late  free  reniform  to  46  late  free 
globose  varieties.  This  table  is  given  as  a  step  in  the  direction  of 
future  investigations  along  this  line,  whidi  appear  warranted  ])y  the 
correlations  found  to  exist  between  the  form  of  glands,  the  date  of 
uiaturity,  the  date  of  bloom,  etc.,  and  the  little  or  great  susceptibility  of 
varieties  to  curl  and  mildew.  Such  facts  may  prove  of  niucii  impor- 
tance when  taken  in  connection  with  future  work  in  originating  hardy 
or  otherwise  desirable  varieties  bv  cross  breeding:. 


^00    PEACH  LEAF  CURL:  ITS  NATUEE  AND  TREATMENT. 

The  preceding  records,  showing  the  comparative  susceptibility  to  curl 
of  iiearh^  200  varieties  of  peaches,  will  enable  the  grower  who  contem- 
plates setting  an  orchard  to  make  his  choice  of  varieties  advisedly. 
As  already  said,  however,  many  superior  varieties  are  very  subject  to 
curl,  hence  the  practical  methods  of  preventing  it  as  detailed  in  this  bul- 
letin make  it  possible  to  successfully  grow  the  most  susceptible  varie- 
ties in  the  most  unfavorable  situations,  so  far  as  this  disease  is  concerned. 
Such  varieties  are  in  fact  saved  to  the  peach  industry  of  large  sections 
of  the  country  by  means  of  this  preventive  treatment.  The  Elberta, 
a  favorite  in  both  the  East  and  the  West,  and  the  Lovell,  a  favorite  in 
California,  ma}'  now  be  cultivated  to  an}^  desired  extent  in  regions 
from  which  they  have  heretofore  been  practically  excluded  b}^  curl — 
advantages  that  are  certainly  not  the  least  of  those  arising  from  the 
recent  work  in  the  treatment  of  that  disease. 

As  a  striking  illustration  of  what  has  just  been  said,  the  following, 
contained  in  a  letter  recently  received  T)y  the  writer  from  a  gentleman 
in  northern  California,  is  given:  He  states  that  the  Lovell  variety 
will  curl  in  his  locality  so  as  to  be  of  little  use,  if  not  sprayed.  One  of 
his  neighbors,  who  had  a  small  orchard  of  that  variety,  stated  that  he 
intended  grafting  the  trees  to  some  other  peach,  as  the}'  did  so  badly 
on  account  of  curl,  but  our  correspondent  advised  the  winter  use  of 
Bordeaux  mixture,  cautioning  the  grower  to  spray  his  trees  thor- 
oughly. This  was  done,  and  the  trees  bore  a  fine  crop  of  fruit.  The 
work  was  so  satisfactory  that  instead  of  grafting  over  the  Lovell 
variety  a  block  of  Fosters  was  grafted  to  the  Lovell,  the  variety  with 
which  the  detailed  experiments  of  the  writer  were  conducted  in  the 
Sacramento  Valley  in  189-4:  and  1895. 

TREATMENT   OF   NURSERY    STOCK. 

The  nursery  is  not  only  the  source  of  the  orchard,  but  also  very 
largely  the  source  of  orchard  diseases,  and  its  health  is  therefore  of 
common  interest  to  the  oi'chardist  and  nurseryman.  Cou'W  a  nursery 
be  freed  from  curl,  many  orchards  planted  from  it  "would  not  suffer 
from  the  disease  for  years,  especially  if  isolated.  There  is  little  doubt 
that  curl  has  been  largely  disseminated  throughout  the  world  by 
means  of  nursery  trees. 

It  has  been  supposed  that  the  main  source  of  spring  infection  of 
trees  was  from  the  perennial  mycelium  already  in  the  Inids,  and  were 
this  hypothesis  true  nurserymen  could  scarcely  hope  to  procure  buds 
for  their  seedlings  whi'ch  were  free  from  this  disease.  The  spray 
work  upon  curl  has  shown,  however,  that  the  single  external  applica- 
tion of  a  fungicide  is  sufficient  to  prevent  95  to  98  per  cent  of  curl 
when  the  treatment  has  been  thoroughly  made.  This  appears  to 
indorse  the  view  that  at  least  98  per  cent  of  the  spring  infections  are, 
as  elsewhere  claimed  in  this  ])ulletin,  from  spores  upon  the  tree,  prob- 
ably largely  resting  upon  or  within  the  bud  scales  themselves. 


TREATMENT    OF    Nl'RSERY    STOCK.  201 

The  facts  given  jue  sufficient  to  wurraiit  some  genei*al  considera- 
tions and  vecomniendations: 

(1)  The  trees  from  Avhich  buds  are  to  be  selected  should  be  thoroughly 
sprayed  with  strong  copper  sprays  before  the  buds  are  removed.  (2) 
Where  the  last  j^ear's  branches  are  removed  as  a  whole,  the  buds  to  be 
cut  out  while  budding  is  in  progress  in  the  nursery,  the  bud-bearing 
shoots  should  be  thoroughly  dipped  once  or  twice  in  a  well-made  Bor- 
deaux mixture  before  being  taken  to  the  nursery.^  (3)  After  the  nurs- 
ery trees  are  budded  they  should  be  sprayed  with  Bordeaux  mix- 
ture, no  portion  of  the  tree  or  newly  inserted  bud  being  omitted.  This 
treatment  should  be  repeated  as  often  as  found  advisable,  and  the  more 
thorough  the  better,  especially  after  the  removal  of  the  seedling  top. 

The  writer  feels  that  these  recommendations  are  for  the  best  inter- 
ests of  the  nurseryman,  as  well  as  the  prospective  purchaser.  The 
Bordeaux  mixture  will  not  only  prevent  the  injurious  action  of  the 
disease,  but  will  increase  the  diameter  and  height  of  the  trees  more 
than  sufficient  to  warrant  the  outlay,  and  will  make  them  in  every  way 
more  valuable  to  the  nurseryman  and  orchardist." 

Messrs.  Dressel  Bros.,  proprietors  of  the  Hart  Nurseries,  Hart, 
Mich.,  sprayed  their  peach  nursery  in  the  spring  of  189i  with  Bor- 
deaux mixture.  They  reported  good  success  from  this  work  in  the 
control  of  curl.  In  the  spring  of  1895  they  undertook  an  experiment 
with  the  use  of  5  pounds  of  copper  sulphate,  10  pounds  of  lime,  and  45 
gallons  of  water,  this  experiment  including  110,000  nursery  peach  trees 
one  year  old  and  of  several  varieties.  The  sprayed  trees  were  treated 
twice,  the  first  spraying  being  done  April  1  and  the  second  April  16. 
On  July  21  the  foliage  of  sprayed  and  unsprayed  trees  was  estimated, 
and  it  was  found  that  while  none  of  the  leaves  had  fallen  from  the 
sprayed  trees,  15  per  cent  had  fallen  from  those  unsprayed.  There 
were  100,000  sprayed  trees  and  10,000  unsprayed  trees  in  this 
experiment. 

Dressel  Bros,  state  respecting  this  experiment  that  they  considered 
the  work  very  successful,  that  their  nursery  stock  showed  good 
results,  and  that  the  work  would  be  continued.  The  spra}  ed  stock 
showed  an  increase  in  height.     In  1897  they  again  treated  their  trees, 

*  This  is  a  matter  calling  for  careful  and  detailed  experiments.  It  should  be  com- 
paratively easy  to  dip  such  shoots  one,  two,  three,  or  four  times,  and  to  have  the 
buds  frorri  such  shoots  inserted  in  seedling  trees  of  separate  nursery  rows.  By  such 
method  a  record  could  be  kept  of  the  number  of  trees  showing  curl  upon  the  push- 
ing of  the  first  leaves.  In  this  manner  much  could  l)e  learned  about  the  disease,  and 
a  standard  could  be  determined  for  the  treatment  of  the  shoots  to  be  used  as  the 
source  of  buds. 

^In  relation  to  the  added  size  and  weight  of  sprayed  over  unsprayed  niirsery  trees, 
the  reader  is  referred  to  Bull.  No.  7,  Division  of  Vegetable  Pathology,  U.  S.  Dept.  of 
Agr.,  1894.  This  bulletin  relates  to  the  effect  of  spraying  with  fungicides  on  the 
growth  of  nursery  stock. 


202    PEACH  LEAF  CUEL:  ITS  NATURE  AND  TREATMENT. 

leaving  unsprayed  trees  for  comparison.  The  trees  of  the  sprayed  block, 
it  is  stated,  were  very  nice  and  straight  and  made  a  good  growth,  and 
there  was  no  curl,  it  being  hard  to  find  a  leaf  affected,  while  growth 
started  well  and  continued  thrifty  throughout  the  season.  The 
unsprayed  trees  on  the  other  hand  curled  so  badly  that  manj^  were 
crooked  and  stunted,  not  attaining  the  height  of  the  sprayed  trees 
within  a  foot,  and  a  good  many  were  worthless.  The  treated  tre^s 
were  spraj^ed  twice  in  the  month  of  March,  1897.  They  note  that 
Bordeaux  mixture,  to  do  its  work  properly,  should  be  on  the  trees 
for  seven  or  eight  days  without  rain. 

SUMMARY. 

(1)  Peach  leaf  curl  haa  a  world-wide  distribution,  occurring  in  every 
region  in  which  the  peach  is  grown.  In  humid  localities  it  is  a  leading 
hindrance  to  peach  culture,  and  in  portions  of  the  Pacific  coast  States 
it  has  greatly  limited  the  extent  of  the  industry. 

(2)  The  orchard  losses  from  peach  leaf  curl  vary  from  a  small  amount 
L  of  fruit  to  the  entire  crop,  while  in  many  instances  young  trees  are 
C  killed.     The  national  losses  from  this  disease  will  amount  to  $3,000,000 

'  an  n  ually .  ^ 

(3)  Curl  is  ca.usedhj a'pa.ra.sitictu.nguslu^own as Mcoascicsde/hr mams, 
the  ravages  of  which  are  largely  dependent  upon  the  atmospheric  con- 
ditions prevailing  while  the  trees  are  leafing  out.  Rains  and  cold 
weather  at  that  time  tend  to  increase  the  severity  of  the  trouble  by 
favoring  the  growth  of  the  parasite  and  interfering  with  the  proper 
functions  of  the  host.  For  these  reasons  orchards  near  large  bodies  of 
water  and  in  low  or  damp  situations  are  more  subject  to  curl  than 
those  in  dry  regions  or  in  elevated  situations. 

(4)  Most  of  the  spring  infections  of  peach  leaves  are  due  to  the 
spores  of  the  fungus  and  not  to  a  perennial  mycelium,  as  formerly 
held,  hence  the  efficacy  of  sprays. 

(5)  Curl  was  first  successfully  treated  in  California  during  the  period 
from  1880  to  1885,  the  success  depending  upon  the  application  of 
fungicides  to  the  dormant  trees.  The  disease  was  not  successfully 
treated  in  Europe  for  ta^  years  after  its  prevention  in  the  United 
States. 

(6)  The  copper  sprays  are  now  found  to  be  more  effective  than  the 
sulphur  or  other  sprays  first  used.  Of  the  various  sprays  experi- 
mented with,  Bordeaux  mixture,  in  the  proportion  of  5  pounds  copper 
sulphate,  5  pounds  lime,  and  45  gallons  of  water,  gave  the  best  results, 
the  equal  weights  of  the  copper  sulphate  and  lime  being  most  effective 
when  the  mixture  is  applied  shortly  before  the  opening  of  the  blossom 
buds.  When  it  is  desired  to  increase  the  durability  of  a  spray  by 
increasing  the  proportion  of  lime,  the  application  should  1)e  made 
earlier  or  equal  proportions  of  copper  and  lime  should  be  maintained. 


SUMMARY.  203 

The  total  saving  of  foliage  increases  with  the  increase  of  copper  sul- 
phate when  the  amount  of  lime  remains  constant,  but  the  average 
saving  per  pound  of  copper  .sulphate  decreases  with  the  increase  of 
copper  used. 

(7)  In  the  treatment  of  peach  leaf  curl,  from  95  to  98  per  cent  of  the 
spring  foliage  was  saved  by  spraying.  A  net  gain  of  600  per  cent  in 
foliage  over  that  retained  ])y  adjoining  unsprayed  trees  resulted  in  the 
case  of  several  different  sprays.  Bordeaux  mixture  when  applied  to 
the  dormant  tree  increased  the  weight  and  starch-producing  power 
of  the  leaves,  and  the  sprayed  trees  showed  a  great  gain  over  the 
unsprayed  in  the  number  and  quality  of  the  fruit  buds  they  produced 
for  the  following  year,  the  gain  in  the  number  of  spur  buds  being  over 
100  per  cent  in  some  cases.  The  lower  limbs  of  sprayed  trees  showed 
a  marked  gain  over  those  of  unsprayed  trees  as  compared  with  the 
upper  limbs  in  both  the  number  of  fruit  buds  and  lateral  shoots  they 
produced. 

(8)  The  average  value  of  the  fruit  per  tree  in  rows  treated  with  the 
most  effective  Bordeaux  mixture  ranged  as  high  as  $6.20  above  that  per 
tree  in  adjoining  untreated  rows,  or  the  equivalent  of  a  net  gain  of 
^27.80  per  acre  where  trees  are  planted  25  by  25  feet.  Over  1,000  per 
cent  net  gain  in  the  fruit  set  has  resulted  in  the  use  of  some  of  the 
more  effective  sprat's. 

(9)  The  trees  should  be  sprayed  each  season,  as  the  experiments 
*  proved  that  treatment  one  season  will  not  prevent  the  disease  the 

following  3'ear.     Spraying  should  also  be  done  even  though  the  trees 
ma}^  not  be  expected  to  bear,  as  the  loss  of  the  crop  of  leaves  is  shown 
to  result  in  as  great  a  drain  upon  the  trees  as  does  the  maturing  of  / 
one-half  to  two-thirds  of  a  crop  of  fruit.  '/ 

(10)  The  work  demonstrates  that  peach  leaf  curl  may  be  cheaply 
and  easil}^  prevented  in  California,  in  western  Oregon  and  Washington, 
and  along  the  east  shore  of  Lake  Michigan,  where  curl  causes  great 
loss,  as  well  as  in  all  other  peach-growing  sections  of  the  United  States. 

(11)  The  copper  and  lime  sprays  are  less  injurious  to  the  trees  than 
those  composed  of  sulphur  and  lime.  The  use  of  lime  in  winter  spra3's 
^as  proven  an  advantage  in  enabling  the  workmen  to  see  their  work 
and  complete  it  with  greater  thoroughness  than  would  otherwise  be 
possible.  A  proportional  increase  of  l)oth  lime  and  copper  sulphate 
is  recommended  for  wet  regions,  and  for  very  wet  localities  a  second 
winter  spraying  is  advised. 

(12)  Cyclone  nozzles  with  lateral  or  diagonal  discharge  are  best 
adapted  to  the  work. 

(13)  The  proper  time  for  winter  spraying  and  the  number  of  appli- 
cations depend  to  some  extent  on  the  locality,  season,  etc.,  but  active 
sprays  are  likely  to  do  most  good  if  appli(Kl  from  one  to  three  weeks 
before  the  opening  of  the  blossoms  in  spring.     The  proper  time  to 


204    PEACH  LEAF  CURL:  TTS  NATURE  AND  TREATMENT. 

apply  sprays  for  the  prevention  of  curl  is  in  dry,  calm  weather,  and 
during  the  middle  of  the  day,  in  order  to  ayoid  dew  or  frost  upon  the 
limbs  as  much  as  possible. 

(14)  Of  nearly  200  peach  and  nectarine  varieties  considered  with  a 
view  of  determining-  their  comparative  susceptibility  to  curl,  it  was 
found  that  very  few  were  wholly  free  from  the  disease  and  that  some 
were  very  subject  to  it.  Some  of  the  choicest  yarieties,  as  the  Elberta 
and  Lovell,  are  seriously  affected,  but  it  has  been  demonstrated  that  a 
single  winter  treatment  will  prevent  the  disease  upon  even  these  varie- 
ties. It  may  be  thus  fairly  claimed  that  the  spraying  methods  recom- 
mended will  save  to  the  peach  industry  some  of  its  finest  yarieties,  as 
well  as  result  in  the  saving  of  foliage  and  crops  already  indicated. 

o 


DESCRIPTION  OF  PLATE  XXVI. 

A  suitable  outfit  for  si^raying  small  orchards.  One  horse,  -two  men,  and  a  lioy 
spray  two  trees  at  a  time.  This  scene  I'epresents  the  exjierimental  spraying  outfit 
used  by  the  writer  in  the  Rio  Bouito  orchard. 


Bull.  20,  Div.  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture, 


Plate  XXVI 


DESCRIPTION  OF  PLATE  XXVII. 

Spraying  4  trees  at  a  time,  with  5  men  and  2  horses.  There  is  here  used  a  300- 
gallon  spray  tank  and  long-lever  (Gould),  brass-lined  piston  pump,'  which  has 
sufficient  capacity  to  supply  4  nozzles,  1  man  pumping.  The  horses  are  protected 
by  means  of  guimy  sack  covers.  The  C'liinese  liats  in  use  furuisli  good  protection 
to  the  eves  and  neck,  but  are  too  stiff  for  the  most  convenient  work  under  Hni1)s. 


Bull.  20,  Div.  Veg.  Phys.  &  Path.,  U.  S.  Dept.  of  Agriculture. 


Plate  XXVII. 


DESCRIPTION  OF  PLATE  XXVIIL 

Regular  winter  spray  work  in  the  Rio  Bonito  orchard.  Eight  trees  are  here 
being  sprayed  at  one  time,  witli  10  men  and  4  horses.  The  trees  l)eing  treated  are 
well  advanced,  the  buds  being  much  swollen,  although  not  yet  open.  If  work  is 
thoroughly  done  at  this  stage  of  bud  development  the  results  will  commonly  prove 
satisfactory;  but  an  active  spray  should  be  used,  such  as  the  eau  celeste,  or  Bordeaux 
mixture  with  a  low  percentage  of  lime  and  high  percentage  of  copper  sulphate. 
Such  sprays  should  not  be  applied,  however,  after  the  opening  of  the  blossoms. 
Earlier  si>raying  is  better,  the  chemicals  in  such  cases  doing  less  harm  to  the  tree  and 
having  a  longer  time  to  reach  all  spores  that  endanger  the  new  growth. 


rSutsS. 


Bull.  20,  Div.  Veg.  Phys.  &  Path.,  U.  S.  Dept   of  Agriculture. 


Plate  XXVIII. 


Z    r 


'i.     O 


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\-,  ^\, 


^^;^-^^^^3:, 


s^.    ...  ,V^i^..: 


■/ 


V 


DESCRIPTION  OF  PLATE  XXIX. 

A  power  sprayer  in  use  in  a  young  orchard  at  Santa  Barbara,  C!al.     This  sjirayer 
was  l)uilt  by  the  Union  Gas  Engine  Company,  San  Francisco. 


